On the free estimate side, you have low ball type contractors and premium service SWAG type contractors. The low baller comes in at a low price. He is likable and seems experienced, but look out! That price will not stay low. And/or, the timeline will never line up with preliminary claims. Jobs may drag out months or years too long.
On the other end of the free estimate spectrum, you have the premium guys. They do perform great, they have a great reputation, and they have become quite adept at SWAG! Scientific wild a—guess. Yes, this is a real thing in the contract world. Many successful contractors are just good at guessing. And they provide good service and quality. The problem is that to be successful, a swag artist must always be high.
The math is simple for a skilled SWAG artist. Talk to enough homeowners, SWAG it high, and some will buy.