When you get a quote for a job, be sure that you are comparing the same things. For instance, many contractors will giving you a low price to get the job, and then balloon it when they have you signed. Be sure that everything that you want from the start is included in your quote. Of course, as you go, YOU may decide that you want to upgrade things; that is different. But make sure that all the work is listed as what they will do from start to finish so you know you are comparing the quotes for the entire job.
Also, make sure that all the prep work is going to be done right with the right materials. For instance, there are setting materials that you can get at the box stores for $7 a bag. If he is using those, the price will be much lower than someone like us who uses the ones that cost $26 a bag. The reason is, the $7 bag will last 1-3 years, the better one will last for the lifetime of the tile. If you are putting the money into it, do it right the first time. Your tile is only as good as the base.
When we first moved here from NJ our first jobs were repairs of 2-3 year old floors, whose thin wood base and cheap thin set could not hold the tile. The tiles then cracked, the grout cracked out, and the tiles were actually loose on the floor. We use cement board under every tile floor, the best thin sets, and also use thin set under the cement board as well as nail it to the floor so that the bond is true and strong and squeak-free. It costs a little more but it is the right way to do it. That way you have a job that will last 20-40 years. We build our reputation on doing it right the first time!