$40. But there isn't a concern about the threads on the poly chugger head since they are NPT and known to be durable. The point that was being made is that if you were going to get the kegking pump, and decided to go with the SS head just because you wanted to be sure that you wouldn't have issues damaging the threads (since they are very close, but not exactly NPT). You would be better off with the poly head chugger which doesn't have concern about thread matching and is a little higher performance for the same price. If there is some reason for you to get the SS head other than the threads, yes, the SS chugger is more expensive.
I'm also going to bet that anyone who is dead set on SS for their pump and is willing to spend a few extra dollars for it is also going to want a pump that is more proven and has an established vendor network in the US. (Personally, i think that's going to be worth the extra $40 to me right now).
I'll certainly be keeping my eye on these pumps in the future though.