We’ve had a thread before about the varying levels of quality in Hosted Games.
As is, this seems like it’s becoming a circular argument. You can’t actually know how much effort was or wasn’t put into a game, and I’m not sure how polling the community would go for unpublished games. Generally the folks participating in betas of completed games are folks who already enjoy and are interested in the final product, so probably unlikely to tell an author their game is worth less.
And I’m not sure what issues could come up in late game that are both not present in the demo and not too subjective to base a pricing model on. And if someone played a demo, bought the game, and felt like the back half wasn’t very good, well that’s the risk you take when buying media. I’ve bought tickets to movies that I didn’t think lived up to the trailer too, or books that I read the back of and then didn’t enjoy. There’s not really a surefire way to prevent it