Some early access games on Steam even come down in price as they get closer to release. Generally these are games that were initially funded on Kickstarter, have subsequently been added to Steam's early access program, and thus use the original Kickstarter pricing structure to be fair to their original backers. This seems perfectly fair to me but that doesn't stop entitled idiots on the Steam forums from ranting about how they're being ripped off (before they've even purchased it, natch). I wonder whether you're serious when you suggest that you should only have to pay "a fraction" of the final price for a game that's released while it's in beta.
In Australia, AAA games often sell for more than $100 in stores, even the ones that have five hours of gameplay and no replayability. $40 indie titles that were made by people who love making games don't sound so bad any more do they?
Ultimately the way they run their pricing structure is their business. If you don't think it's good value, don't pay for it. I value games by the enjoyment I get out of them, not who made them or how much money went into their production.