Sounds kinda high in price to me but don't know your area. I had a 180 by 80 ft pond max depth 8 ft dug with a good backhoe operator for 2800.00 55.00 per hour give or take. I didn't need the dirt but a neighbor did and paid about 1500.00 for a trackhoe operator and 2 semi-dump trucks to move the dirt so for about 4500.00 my pond was dug. Double that and your looking at 9000.00 so I think you should be able to get it done for less than 15K . Just my thoughts.

Bob