What I meant was, if EA gives you 1/3 of the game's content to try and comment on, then one option might be to pay 1/3 of the price just for that content. When the full game comes out, you pay the remaining 2/3 of the price to "upgrade" EA to the 1.0 release. The cost for the full game is the same ( no-one gets the full game cheaper ); the only difference is that if the full game does not turn out to your liking after feedback from EA, you needn't purchase the "upgrade" to the full game.
As I said, I don't expect this to happen, and consequently their feedback may be limited to those people very enthusiastic for what they see already.
I don't think they have any incentive to do that. You would sell something for $20 if someone was willing to pay $60 for it, even if that 'something' was unfinished? It's not a trial offer; it basically a pre-order that you can playtest. As for the feedback, I don't see any reason to believe that the 'very enthusiastic' people (as a whole) won't be able to offer good constructive criticism. I also expect they are likely to put more time in testing the game than people who aren't so enthusiastic. On the flip side, a $20 EA could easily see an influx of nay-sayers. haters, trolls, etc. who will pass judgement on the game for ridiculous reasons (e.g bugs or lack of desired elements like RTwP).
