Maternal incubation is free, but a lot of herpers are against it, as some believe it to be stressful on the brooding female. The cost of incubators vary. Hovabators are around $40 but are prone to let temperatures fluctuate during incubation. A popular do-it-yourself incubator includes installing heat tape in a refridgerator or anything else that has good insulation. You can find incubators for sell for $300+