It's $2.39 on GOG (https://secure.gog.com/en/gamecard/sid_meiers_alpha_centauri) right now. Stupid money for one of the best games ever made. I own it but I just bought it again on GOG for the convenience of having it on my shelf, not to mention the promise of it working in Windows 7. 8)
Oops I missed the other thread about the sale. Mods can you delete this thread please?