Personally, the tension that I have in dealing with contractors is not wanting to be taken advantage of. Much in the same way that mechanics and used car salesmen are 'notorious' for taking advantage of people.
At the risk of sounding inflammatory, many home owners want everything cheap as humanly possible, so they find people willing to do it for below minimum wage (immigrants) and buy the cheapest, warped material they can find at Home Depot. Sometimes spending a little extra money for expertise is worth the sacrifice. You are, after all, paying for a service that affects the most important piece of property you own, and you may have to live with a regret for 30 or more years.
Now days, you can get references, see photos of prior work, and of course someone with high quality tools (not Craftsman) and a truck is likely to be a better choice. Someone that is willing to say "no" to you is also a good sign.