Not sure why I would want to spend $73 for an "open all around" one temperature plate (and potentially another $29 for a cover so they don't stand and poop on it) when I can buy a heating pad of nearly equal size with 3 temperature settings for less than $18 and make a very adjustable shape cave with a leftover piece of wire fencing and an old pillowcase. Each chick can get as close or far from the pad as they like depending on their current need for heat unlike a rigid plate which is a single height - probably somewhat adjustable, but not likely to the 2" difference front to back of a MHP cave.
And the heating pad has uses when not brooding chicks, unlike the single purpose heat plate.
It was just a suggestion. The plates will last for years and are a good investment. I predict that those using the pads will want to get a plate one day.
You are of course comparing a plate that can cover 60 chicks with the cost of a heating pad that will cover 15 though. The plate that covers 15 chicks will cost you $10.00 more than the pad and the pad will not last as long. It is called the economics of disposable things compared to durable goods.
You get what you put into things sometimes. I see a parallel between the heat pads and those that use a low quality incubator and then have bad hatches--then wonder why they have bad hatches.