It looks like there are 4 levels of pricing for XBLA games? 

400 points

800 points

1200 points

1600 points

Should Microsoft have different achievement allocations for the price points?

Maybe:

400 points - 200 Achievement points in up to 12 achievements

800 points - 200 Achievement points in up to 12 achievements

1200 points - 300 Achievement points in up to 15 achievements

1600 points - 400 Achievement points in up to 20 achievements

No. People should pay for quality/content, not achievements.

Yes, that sounds good. Also, xna games should have 100.

It doesn't have to be either/or. Why can't people pay for both quality/content and achievements? Some games, depending on length and playability, shouldn't have more than 200. Others should.

Agreed.

i buy xbla games for fun not achievements

Agreed, says Mr. Avatar TLA:TBE/Sealife Safari :P

I think arcade games should have more gamerscore, especially the games which have add-ons too.

I wish some Arcade games could have 1000 pts cause some of them are much harder to get the 200 pts than it is to get 1000 in a retail game