I guess the most important question here is, what did your quotes come in at?
The concrete alone is $3/sf (6", not including markup), then some mesh or rebar at another $1, then forming at a few bucks, then pouring at a few bucks. Is it already graded and ready to go? That will cost you more of course. You want rock beneath it? That is another $2/sf for material and more for labor. As mentioned above, you tailgating or pumping? Pumping is more.
You may pay more for the mud if you have a short load..
It's probably best you just get a quote..