Nice trio of Fieros. I really don't think he is off base with his price for all 3. If I had the spare cash (and a place to put them) I'd offer up $25K. I'd probably flip the yellow one and keep the other two.....I've never owned an Indy before and I love the red with tan interior (just needs gold wheels to be 'perfect'.
If they were manuals instead of autos he might have them sold already (I've seen that ad before).
The Indy will likely become the most valuable of the lot. It's going to get harder and harder to find Indy Fieros in that great shape in the next decade. You can always swap parts around in '88s and such and get any combination of a car, but as original Indy pieces are getting more and more scarce - especially original interiors not all beat to hell and back - then yes there could be some potential value.
Indeed it would be cool to see if he could take $25K-ish, and then subsequently off-load one of the GTs (it could easily range $6K-$8K with the right buyer). I'm in the same mind-set above that I'd probably keep the red one as I too like the gold wheel / red body color combo. Eventually when the Indy appreciates a bit more dump it off or just keep it.