Certainly sound high to me unless she is talking a fully finished basement, or you are in a high water table or expansive soil area where a fully reinforced concrete foundation and full structural waterproof basement slab and underdrain system will be needed.
Roughly speaking, going to a basement instead of a normal crawlspace adds $10-25,000 to a normal house (for 1000 SF basement size range) depending on how deep the foundation has to be anyway in your area for a crawlspace (because of expansive soil or frost penetration), and a full unfinished basement versus a slab on grade about $15-30,000 additional. Of course, if you have a complex house layout with lots of foundation corners, cost goes up.
I would (presuming you are talking a specific house or house plan) ask for a written quote on that house with and without full basement - and specify if you mean unfinished or fully finished.
