upgrading your HD on your XBox for another $100 or so vs. buying a $2000 gaming computer, what makes more economical sense here?
The good news is I'm 100% positive you can buy a computer that will run TOR for $600 or so, at best I'd guess. Only because I'm looking at new PC's right now, and they're really cheap compared to the last time I bought a new PC... Even the high-end stuff from a private seller I've looked at wouldn't cost me $2000 unless I was taking the tip-top technology on the market and maxing out RAM, HD, etc.
Computers are basically cheap, at least compared to the good old days when you DID need a super system to run games (oh the old X-Wing days, how I long for quality games like that!).
So having a PC to run it is pretty affordable to the vast majority anyway... I think the mouse/keyboard thing seems pretty simple to fix though on an X-Box, so that's a lame excuse it seems.
Still, like I said, you can't take the XB with you really... And those games really take a lot of time I guess.

Almost everyone I know who plays WoW does so on a laptop so they can take it to watch TV while they play, or even on vacation... That's, to me anway, a huge factor.
The XB's Harddrive I can see being an issue too, if you store a lot on your XB's HD. That's relative though... I don't, but I know people with practically full HD's or have had to buy an extra. That all depends on the gamer then I guess.
I don't know what kind of memory needs are there for saved characters too and things. People can make a lot of characters on one account though I guess, or something like that. So there's that to consider I guess. *shrugs*
For me, if it played well on the XB360 I'd play there I'm sure, but as it stands I'm just factoring it in while I look at new PC's and decide what I'm going to do. Even the base systems I looked at should run the game though, ironically.