For a Milspec M4 which has 3 round burst, and a milspec M4A1 which has full auto? Not at all. I’m actually quite impressed by that price. A partial milspec low budget semi auto civilian version like the DPMS Oracle is probably close to $500 right now
I don't think the price is out of line. Given the option, I'd pay that much for one. I'm fairly thrifty, so I see the price of a full auto or three-round burst capable mil spec firearm for a dab over half the price of an M1A as a good deal.