The cheaper Aperture makes sense.
1) You can't "share" it with your friend. Yes, full-out piracy still exists but that's always been a small percentage of users. This attacks that big grey "middle ground" of people who wouldn't outright steal...but still share with that 1 friend you have. That alone could make it worth the lower price for Apple.
2) You can't re-sell it. It's tied to your account. You own it and ONLY you own it. This means less E-Bay sales and more Apple software sales.
3) I'm guessing there won't be upgrade prices for this. Just like iLife has been in the past.
Put all that together and you get $80 instead of $200.
And you know what? I'm ok with all that. #2 and #3 sound bad, but I like the idea of cheap software every year rather than long chain of "very expensive" + upgrade + upgrade + upgrade. It gets tedious to have to keep all this old stuff "just in case I need the last 5 codes for my next upgrade!"
And besides, this is ALL worth it for the fact that I can install this stuff on ALL my Macs without feeling like a criminal! This is the biggest shift here...sell software for USERS, not for MACHINES. I always buy the 'family' pack of stuff when it's available because I feel guilty, but I still feel ilke I'm getting ripped off 'cause I'm sure the single-pack users are putting their software on multiple Macs anyway. Good riddence to that.
And I don't have numbers but I really do think the impact of #1 is huge. I mean REALLY huge. This may end up being even more important for small software companies than it is for a company like Apple. They've had fewer resources to protect their software in the past. The Mac App store may be a gift from heaven to them for this reason alone.