It's hard to make a fair offer without knowing the conditions of the plants and how they have been grown recently. Pictures would help. I looked at her post on Craigslist and she says they have been neglected and probably won't bloom for her, but these remaining ones are in the "best" condition. Her honesty is admirable, but I don't think you will see much interest, with the exception of a local buyer who can see what they are getting. Perhaps taking them to a club in her area would put her in touch with buyers who can offer a fair price.
Ann

Great! First step a link to a site with detailed photos of the plants. Keep the ideas coming.

I agree with gardnergal, without seeing the plants, it's hard to make a judgement as to worth. However, most of the plants listed are fairly common and have no clonal or varietal name. If they were awarded or "famous" plants that's something. It's easy to get price quotes for these. If your friend belongs to a local orchid club, she can try and sell them there. In the end, if there is no demand for these plants, donating them to the local orchid society is the best thing to do.

I think she is working to get images up on a website. I appreciate the comments and interest that have come from this site.

If you want the plants to actually leave your possession, $15-$20 per healthy plant unless it is a truly rare, expensive plant. In bloom add $5.

Experienced hobby growers who know the value of plants generally get most of their rare plants from friends as free divisions or trades. Or they know the places online to get them. No real orchid grower will pay high box store-garden center prices. For novices and the general non orchid public orchids are like cars, once off the lot the price plummets. A $50 florist's blooming white noid Phal is worth $5 on the street out of bloom.

Two people can sit side by side selling orchids, one a private collection, and the other a professional vendor. Same plants. The vendor will get $5-$10 more per plant and sell twice as many because people think they are "new cars". I've sat in both chairs. It's very frustrating