Like TomKerekes I'm also stunned by that quote!
I've had plenty of 500 Q batches done, either for my products or for clients. I would expect $150 to $300 one-off cost for solder stencil depending on size and brass or stainless. Then maybe a $200 setup fee to load the machine then on 500 Q PCBs about 5 cents to 10 cents per component for SMD placement and solder and inspect. That depends on type, larger simple components (0805, SOIC) are cheap, things like tiny parts or fussy fine pitch chips (SSOP) will slow the machine down and bump the price.
So for 500 large PCBs with say 100 parts per PCB I would expect about $200 + $200 + (500 * 100 * $0.05) total about $2900, and possibly less because generally once the price gets over $2k it gets a bit negotiable. If they were small PCBs with 25 parts that total would be maybe $1200?
Most machines will do an easy 2000 parts/hour and even at 5 cents a part they make real good money per hour. A place with a fast machine and higher quantities can get down to 2 cents a part. Those are local prices, Asia will do much cheaper but quality may suffer and the wait time and hassles grow.
Please don't think I'm criticising your purchase of a machine, it's wonderful to have machines in house.
But it's also wonderful to mail a carton of reels and empty PCBs out, and two weeks later receive back a carton of finished inspected PCBs and your leftover parts.