In the digital era, there are dozens of ways to measure success in the music industry: YouTube views, Twitter followers, download single sales, tour receipts and yes, album sales. That last number, though, has become one of the most slippery of all lately, as music fans have more and more ways to experience their favorite artists without necessarily paying full price for a traditional record.

The latest example of that principle is Lady Gaga's ARTPOP. Arguably one of the biggest pop stars in the world, capable of selling out arenas across the globe and one of the foremost experts in stoking and controlling the hype machine, Gaga's latest project will land at #1 on this week's Billboard albums chart with sales of 258,000.

For any other artist these days, that's a solid, if not spectacular, opening week. But for Gaga, who spent months playing shows, putting on an ArtRave and making appearances for one of the most elaborate, multilayered promotional efforts in recent memory, those numbers had some blogs and critical circles talking "flop." Not to mention the gap with her Born This Way album, which debuted with 1.1 million in sales in 2011.

So, what happened and what does it mean? MTV News spoke to some experts to decode the ARTPOP conundrum.

It's Apples And Oranges

Let's get one thing straight: You can't measure ARTPOP against Born This Way. Back in 2011, Gaga was coming off the slow-burn-into-supernova success of her debut, The Fame (and its sequel, The Fame Monster), which spawned six #1 singles on the Billboard mainstream top 40 airplay chart. That album's mainstream pop/dance appeal instantly made Gaga a cross-platform superstar.

So, it stood to reason that a lot of people would be stoked for Born This Way, which upped the artistry and lowered the accessibility a bit, spawning just one #1 single in the title track. But, Born This Way still moved a phenomenal 1.1 million copies in its first week, nearly half (440,000) of which Billboard magazine estimated were a result of an Amazon 99-cent album promotion. (That sale eventually led to changes in chart eligibility requirements from Billboard based on a minimum pricing.)

"It's really unfair to compare them," Billboard's associate director of charts, Keith Caulfield, told MTV News about ARTPOP and Born This Way. "She would not have hit 1.1 million if not for the 99-cent sale, so there's always that asterisk. That said, it's not terribly surprising that ARTPOP will sell less." (Caulfield and the other experts were speaking before the final ARTPOP figures came out, basing their comments on early projections that were very close to the final first-week numbers.)

After The Fame, Caulfield said Gaga was arguably the biggest pop star in the world, so it made sense that millions were waiting for her next act and showed up that first week. "But does your mother want to buy ARTPOP?" he asked of the more experimental album, which mixes EDM and hip-hop, and makes casual drug and sex references. The promotional rollout was also heavily built on Gaga's collaborations with art world luminaries who may not be household names for all of her fans.

"There was something for everyone on Fame Monster. ... It made her incredibly accessible, but still quirky," Caulfield said. But then some fans felt she was getting a bit out there with Born This Way and, well, maybe this time, he speculated, "she went on a specific path and consumers went on theirs."

Down The ARTPOP Rabbit Hole

"People liked Gaga with the disco stick and 'Paparazzi,' but I think she got too weird and macabre with all the performance art and may have alienated her base," agreed Nicole Sia, managing editor of Spin magazine. She also suggested that first single "Applause," which peaked at #4 on the Billboard mainstream top 40 chart just didn't connect with fans the way some recent #1 singles by other female pop stars like "Roar" (Katy Perry) and "Wrecking Ball" (Miley Cyrus) did.

"As she fell further down the pop art hole, she's become too alien while Katy Perry has gone more homogenous than ever. ... Soccer moms are not going to buy a record for their kids with songs about marijuana addiction," Sia said of tracks such as "Dope."

If Gaga is aiming to go the outsider route and be an avant-garde act with one foot in the pop world, ARTPOP is a good start. But Sia said the "borderline schizophrenic" musical vibe on the album tries to hit too many different audiences without focusing on Gaga's core, dance/pop-loving fanbase. "The first record was wedding music that was good for the gym and bat mitzvah and this one is not for the casual listener anymore."

Singles Artist Or Album Artist?

Hollywood Reporter Music Editor Shirley Halperin said it really comes down to "Music Business 101" theory: If you don't have a huge hit single on radio, it's going to be hard to sell a ton of records.

"She did everything by the book and didn't do anything wrong, but we're at a point where the music industry is just coming to terms with the fact that certain people are album artists and certain ones are singles artists," Halperin said, pointing to the reliably huge singles sales for Perry, Rihanna and Cyrus. "And Gaga, as much as she'd like to think she's an album artist because she creates these avant-garde [objects], she might be a singles artist too."

If you look at the best first-week sales figures so far this year, Gaga comes in at #12, behind huge opens from Justin Timberlake, Eminem, Drake, Luke Bryan and Jay Z. In fact, you have to drill down to #10 and #11 to find Perry and Cyrus, whose first weeks were in the same range as Gaga's.

Halperin said it could be that Gaga was overly ambitious with the concept of the album, which requires fans to think a bit more than they might be used to about her message: "A lot of people don't have a connection to the art world ... and while she has a core audience, a lot of casual fans probably didn't jump on the boat this time and are waiting to hear another single."

Take It To The Stage

Wherever ARTPOP's sales end up, one thing is certain: Gaga's a born performer with a killer stage show. Though no tour dates have been announced yet, all three experts agreed that once she hits the stage, Gaga will almost certainly be back in her comfort zone.

"I don't think five years is enough time to judge what she's managed to do with her career," Halperin said of those who are quick to dismiss Gaga as a comet that has burned too bright too fast. "It's a marathon, not a sprint and if she wants to be like David Bowie, she will evolve and some albums will sell more, some less, some will be more conceptual, some more commercial. This album is a hiccup in her career in terms of sales," she predicted.

Sia also noted that if you look at the just-released Forbes list of the World's Highest Paid Musicians, Gaga is right there at #2 with more than $80 million, much of it from touring. "She's not crying," she said. "She wants to be an album queen, not a singles artist like Rihanna and that's why she has these far-flung concepts. She's more multi-platform — selling her lifestyle, her charity, her tour, TV specials, headphones — I thinks she's got a much bigger reach than a lot of pop stars."

Once those tickets go on sale, Caulfield said he's sure they'll blow out the door thanks to Gaga's live track record. "Some people are like Madonna, who is a live attraction, but is not really selling new music," he said. "But [Gaga's] transitioned really quickly to being a headlining arena act and artists like her — who can do so much in such a short amount of time — don't come around very often."