I'm sure she'll tell you if you ask but I think Kit helped her out with it (we should also hit Spotify soon enough) and that it wasn't too bad for what you get out of it.
If the pricing remains the same, I put one of our albums on TuneCore in 2008 and it was $19.99 per album plus $9.99 per store/arbitrarily-defined-region. The only recurring fee after that is a $19.99 yearly "maintenance fee" (per album) to keep it on file with TuneCore, which essentially means you'll only have to pay if you want to keep it on file with TuneCore for distributing to other "stores" in the future; it doesn't pull the album from the places it's already sold in.
Having a quick look, they may have dicked with the pricing a bit -- but it doesn't make it any easier to understand.
At any rate, cool stuff! There's something way cool about having your own music sold alongside everything else, all proper-like.