Reading the original post it seems to say 1.5K plus "tons of eng time", I'd imagine that it's the opportunity cost of the engineering time that ends up being by far the most expensive part in this and that the 1.5k figure was just the other fixed costs.

"Seems like you would realistically need about 5-10 phone screens plus 1 or 2 in person interviews to fill a position. 3 if your phone screens were really off the mark." Just curious what your thought process is to arrive at these numbers?