So let's say you create an album with 8 tracks. You pay $0.99 per track upload plus another $0.99 for the album listing, and $9.98 for the first year album fee. That works out to--scratches head--8 x $0.99 + 1 x $0.99 + $9.98 = $18.89 to upload and store that 8-track album. After the first year, you continue to pay $9.98 per year per album. That album would start earning money for you after the first 26-or-so sales, if I did the math right which is always questionable.
So what does selling through iTunes get you? First of all, nearly anyone who doesn't use Linux can use iTunes to buy your tracks, so your product is pretty accessible. Second, I'm guessing that TuneCore takes care of a lot of the accounting issues, so you just upload and you're done until you start earning money--if you start earning money.
Obviously, you'd have to take care of your own marketing, but this would make a great way to distribute material for non-profits like schools for audio-only material. This of course, assumes, that TuneCore ends up being reliable and trustworthy. TuneCore offers a complete FAQ of their service here.