That sounds like a fair price to me. You are looking at 33 cubic ft. of concrete, which equates to a little more than a yard. Here in So. WI, a yard goes for around $100. If you just ordered one yard from the concrete company, you would get hit with a small load charge, and that could be a minimum of $300. If I were you, I would make it bigger so you can step out of the tub onto concrete, unless this is going in an existing patio area or something similar. Having to wheel barrow it in place is very labor intensive, and therefore the high price.
On a side note, I was very active on this site last year at this time. I haven't been on much at all, and it sure seems to be dead around here. Maybe Trouble Free Pool is the place to be!
