We're in Houston Texas and looking to have our existing concrete slab patio covered in travertine. 400sqf. They're probably going to need to order more for waste / backup but let's just face it on 400 ft²

I'm getting a few quotes but they're all over the place in terms of labor and install. I've contacted a few outdoor contracting companies as well as an independent guy or two but the price is so much different.

One company whose work I love and does outdoor stuff all the time is $5100 with $3.50 tile allowance including thinset and polymetric sand all in. (About 9.50 labor incl thin set and sand) - I know the job gets done with this guy and perfect but again is it too much

Another independent guy is $1575 for labor/thinset/grout. If I use the same allowance cost as the other guy and buy the tile it's about $1,400 In tile so $2975. (about 3.93/sft In thinset/grout)

That's a big difference so Im a little confused. I want it done correctly and I want to make sure that the pitch of my covered patio stays the same so what it runs off. Just want to be done right