I think what you're saying is you'd charge more for single-engine piston than for single-engine turbine. That might make some kind of sense due to risk assessment, but not from either a cost-of-recurrent-training-and-insurance or what-will-the-market-bear assessment. I can't imagine you getting much work for $1000 a day for single-engine piston in most of the U.S., but if you can, then great.
Yes, I agree that every Commercial pilot needs to be cautious of this, but there's nothing in the OP's post that indicates any reason to be suspicious. I've flown a lot of single-engine piston contract work, day, night, VFR, and IFR, all perfectly Part 91 compliant (flying the owner in his own airplane).
Obviously market and location is paramount here. You're in about the most expensive market in the U.S., higher rates are likely normal there. If you can get 720 (strange number by the way, how'd you arrive at that?) or 800 a day for single-engine piston work, I say go for it! I suspect the market for the OP in West Texas is similar to me in Oklahoma City.