well depends on how many clutches you want it to hold
for 2-3 clutches: a thermostat 70-120 dollars, a cooler like the large igloo coolers, 2-3 foot heat tape, a fan, water bottles, and a thing that you use for egg tubs that light thing where you put the eggs on.
for a 5-8 clutch: a thermostat 70-120 dollars, a broken mini fridge, 2-3 foot heat tap the 11 inch kind or heat rope, a fan or two, water bottles, and thats it.
THe fan for both incubators I dont know yet. Some people have fans and some people dont. If your ambient temperature isnt 87-89 throughout the whole incubator than a fan would be good to regulate the heat.
Everything in total can be around 160 dollars in total i guess. Depends on the thermostat and heat and fan cost. Thermostat people use proportional or the johnson and ranco thermostats. Some people use other on/off thermostats and have had good results. I talked with Brian gundy and he says that the temperatures dont have to be dead on and there can be a few degrees fluctuation.