True coolers are awesome, last year we used a 3 shelf "coke" true cooler and it worked perfect.
$400 total into the Coke cooler t-stat and everything.
In my area they average $200 not working or low on freon on craigslist.
This season I have a larger one for more clutches and my partner took his home, lol.
I have less into this one, due to the cost of the cooler itself being cheaper, than my partner put into the coke cooler.
I don't think you can buy an incubator that will hold as many clutches for anywhere near the same price,
and I doubt it would work any better...