As pezaddict said, ours were letterpress, which made them fairly expensive, but that is true of all letterpress. I think the invitations with envelopes and licensing were about $6 a piece. If I had had custom letterpress anywhere else, the price would have been the same...but you also pay a Disney licensing fee. That can't be avoided, but also was the main reason we wanted to work with Shelley. I have to stress, though, that any invitations you choose will be priced according to what type you want. No one can say "invitations from Impressions cost...such and such."
Shelley does everything very custom, so she can work with you to get the right kind of printing (thermography and offset are much less) combined with a custom design if that's what you want. Also, we opted not to have Disney characters or images on our response cards to cut the licensing costs (you pay licensing per item). She can discuss all cost-cutting options with you.
As you can see on her website, she also has stock invitations that she can offer. We just wanted custom from the get-go, so I didn't explore that option.