call me the minority but i really think this relationship will last or at least going for the long-haul if not marriage.... the reasons lie in several factors
1) the money aspect, R gave up NOT 1 BUT 2 (that's two 99.9999%) chances at a million dollars, I don't know about you but that definitely tells you something about the gal, her having a 'bitchy' personality or not...... and at the same time, Cal gave up his chance at the million (altho it was in fact 50/ 50 and someone here eluded to the fact that his best strategy was to leave that mystery check alone). All of THAT alone tells you about their commitment to eachother.
2) Now the "million-dollar experiment" alone DOES NOT in any way determine the success of a successful lasting relationship, which leads me to the couple's personalities or rather their compatibility. Look we all know what R's deal is from the show.... from the very beginning of this season's FLOM, R is clearly a very picky, very opinionated and not an easy to please person... some might even call her 'bitchy' (me included btw) so for her to give IT, and I mean "IT", all up for some guy she just met for a very short period tells us either she's incredibly stupid (which I highly doubt) or tells us that she knows and sees something about Cal that we, the viewers, don't. For her to make that jump from "greed" to "love" with the kind of personality that R has is really something incredible and serious. And from the side of Cal, he too played his cards right and asked the "right" questions about the future or the possibility of a future in this relationship. He has every right... in fact he NEEDS to be skeptical about R's intentions and he needs to lay it all out for her to see... where they stand and stuff.... and he did that and more, I might add. Even Ryan and Trista (remember them?) didn't have it so good on their show.....
3) Having said that I want to point out something that kind of bugs me in that many home viewers of the show, the majority and myself included, does not have a favorable opinion about R. She's a 'bitch', pure and simple. But that doesn't mean she can't have true love happen to her either. That's what bugs me..... what seems to me that some of you are betting on a-soon-to-be failing relationship or breakup or whatever SOLELY based on the fact that you don't like the girl very much, rather than giving more "realistic" reasons. Look, a 'bad' guy (or gal) can also have a fairly tale ending too! Right?
4) the final reason why I think this relationship will work is because they're a truly compatible couple. Their personalities are similar, their wants and desires and also they seem to be attracted to eachother physically. Even if this union does not translate into marriage, I think the couple's dating relationship will last for a long time to come. They love eachother no doubt about it.