My numbers:
With 90000 hits I assume you mean tgp gallery, so it's about a 1-3% CTR for about 900-2700 hits through to your sponsor. # sales then depends on the how the site converts.
Ramster mentions 3-5% CTR but I haven't seen that in a long time on a tgp gallery.
For freesites I'm around 12-15% CTR.