I do not believe those prices reflect the true market value. This is in that unfortunate situation where the demand is low and the demand is low. So the actual value may be $10-20 for a sealed copy, but there aren't many out there. And because some think that all big box PC games (or software) has a high value (when it doesn't) you have these cases where you can only find copies for $50.
I have a not-sealed, not-mint, but complete copy of 3D Home Architect for Windows 3.1/95 on CD-ROM. No version is specified.
I will buy big box software if I find it, but rarely pay over $6. I would normally say my max price is lower, but I recently paid $6 each for sealed Microsoft Money and Internet Starter Kit.