A burst of activity for such a deserving film on its recently moribund board is encouraging; even more so among people of literacy and consideration. The thoughts in all of the further replies are worthy of response, but it's difficult to separate them, so I'll hitch 'em all here at the end as what I hope will be an only temporary caboose.
Prime's (may I call you that to save keystrokes?) remarks about typical Hollywood endings are apt as they apply to this un-Hollywood movie about Hollywood, and Otter's observation about its cynicism tie them up with pink ribbons (as another great Wilder film had it). As well, Prime has something there about the fragility of the Artie-Betty relationship. While they seem content enough at first glance, there are hints that he's not exactly her grand passion, reflected in her sometimes dismissive attitude ("Oh, Artie, this is shop talk;" "Oh, Artie, shut up"). It's as likely as not that she'll take that train to Arizona not for a two-dollar wedding, but to break it off face to face.
I will point out, Otter, that Joe's "unemployed gigolo" status is something that Betty, with the idealistic stars of romance in her eyes, already resolved to overlook ("I haven't heard any of this. I never got those phone calls, and I've never been in this house. Now get your things together and let's get out of here.") So Joe, realizing his attempt to scare her off isn't working, decides to be cruel to be kind: "Look, sweetie, be practical. I've got a good deal here. A long-term contract with no options. I like it that way."
It's as though Wilder and co-writer Brackett are saying that, in the real Hollywood, there are no Hollywood endings, and unhappiness enough to go around. How appropriate for a film with a viewpoint that's fatalistic in both figurative and literal senses. And how appropriate also that the only one who gets a happy ending is Norma, and hers is a manufactured fantasy of lights and cameras.
I think that saying Artie is "not exactly her grand passion" is a good way to put it. It seems like a case of settling. She sees him as "Mr. Good Enough" and is willing to marry him as a matter of practicality, but she's not actually that into him. It's off-putting how willing she is, essentially from the beginning, to share affections with another man and be unfaithful to the one she's engaged to. There definitely doesn't seem to be a strong foundation there for a healthy and successful marriage.
Regarding there being no Hollywood endings in the real Hollywood, yeah, the film does seem to be almost subversive in that sense. It is as if the filmmakers are trying to pull the curtain back for the audience, and reveal Hollywood for what it really is: A town of human beings, not "stars," who are chasing the life that everyone else thinks they are already living. In Joe and Betty's case, they are chasing something they've never attained. In Norma's case, it's something she once had but has lost and she's desperate to get it back. Even in Hollywood it's only the 1% who actually get to share in the spoils.