I am not in the market, since I don't have the money, and like numpads, but this does not seem out of line.
Considering what these sell for, a pristine specimen, ultra-early date, and original packaging make it extremely desirable. I would think that $300 is not out of line at all.
Of course, the real old-timers are scoffing because they have multiples of these that they bought back in aught-2 for $40