Yes, as Steve says, get at least 3 bids. Then, when you can see the differences, do ask one vs. the other, why there is a difference. In one case, a plumber may be self-employed. Hence, not much overhead. Another guy might use copper vs. PVC. A third bid may be 'who knows'.
Just don't be afraid to ask each of them why one is charging more, or less, than the other. This will educate you. After that, you can pick the contractor that you're most comfortable with. It's good you're open to the price in exchange for 'good work'. I know - that's what we all want.