the price is not the issue!
the law governing construction contracts is very complex and is somewhat
different from the law governing other contracts. for example, do you know
that, by law, you probably won't get any compensation if the builder uses
inferior materials than promised?
a good lawyer can help you to make sure the contract is not one-sided and
help you to avoid future dispute by negotiating the contract terms. A
lawyer probably won't help you negotiate the price.