How much does aircraft deicing fluid cost?

Cheap. Deicing fluid is actually the same as antifreeze or gycol. That's what my local airport used on the small planes when the pilots requested it and it works like a charm! It's a clearish red oily/pastey fluid.

ACTUALLY... real deicing fluid is not Cheap! dumping antifreeze on a small plane MIGHT keep a clean aircraft from freezing for a short period of time, but it will not de-ice it. De-icing fluid is applied between 160-180 degrees. Prices range anywhere from $10-22 PER GALLON. Far from cheap.