As the other poster noted, they are quoting you for a lot of maybes.

But also, a big part of the price is simply supply and demand. There is a shortage of experienced, skilled laborers, and it isn’t going away anytime soon. If you are dealing with an independent contractor, for example, your price needs to not only compete against other potential projects in terms of time/effort, but also must compete against the alternative of “what if I just fucked off and hung out with my friends instead?” The beauty of having experience in skilled labor (right now at least) is that your skills are in short supply, but are largely interchangeable with anyone else with the same skills. So if you were to get fired - or just quit because you don’t feel like working - there is no hurry to find another job. You know you can find another job almost instantly. Which is why I know several contractors who just work summers, and then fuck off and go rock climbing the rest of the year.