Cecil, the $ is in direct correlation to the well pump motor size. A $20 switch rated for a 1/3 hp 120v motor isn't the same as one rated for a 5 hp 220v motor. It may be less $$ than what JKB is talking about, but I'd rather prepare the client for the worst case (money wise) and come in under budget than way over budget.
There's probably cheap ways to do it, but there's no guarantee that the pump motor won't fry.
Just like a clients waterfall/stream pump. The old one stopped working and he wanted a bigger pump for more flow. Sure, I said, but you're going to have to upgrade the wiring going to the pond. O.K. he said, I'll have an electrician out here (his brother). I told him that I thought he should go with at least 10 ga, but 8 ga would be better, but to have the electrician do the calculations to be sure. $1,100 for a 13,600 gph pump. It lasted just shy of 2 years. He's feeding it with a little over 100' of 14 ga wire. (120v) (He didn't tell the electrician that there would be 2 hp on that circuit.)
This year he added a Kasco surface agitator to the same outlet, and the waterfall pump failed. Previously, the outlet wasn't working, but somehow there was still power getting out there. The electrician that was called out said that he had to turn the breaker off, then uncover the whole wire run and let it cool because the dirt was too hot to move with his bare hands.
All the electrician did was fix the "no electric" problem, but didn't upgrade the wires because he wasn't told the load that would be on them.
