A "fair" price for used equipment is pretty hard to determine.

The Ultra Stick and Evo46 is available as a combo from Horizon for $215. The 7C is $250 with PPM receiver and $290 with PCM. His investment is $465 or $505 (at least that's what it would be to buy it today) plus the cost of a 5th servo and a few accessories (maybe $500 or $540 total).

I've seen lots of used stuff (in very good condition) sold for 50% of cost. I've also seen what looked like "junk" sold for probably 80% of cost.

Some of the used stuff auctioned on ebay sells for more than cost (never did understand that).

My best friend and I drag raced a car in the NHRA for a while. When it came time to sell, I asked a few people how to price the car. The most common answer was "Add up the cost to replace every part in the car with no labor added. Divide that in half to get an asking price and work down from there until it sells." It actually sold for about a third of replacement cost.