If it's your business, John, you can pay a lot more if you want piece of mind.
In the public sector, I guess the specs are everything, if that low bid stuff is going to work. Including penalties and sanctions for non-performance.
I use this for work on my house. I put in a bonus if they finsih ahead of time and daily penalties if they're late. Doesn't always work: one guy returned my down payment. But it generally does.