There are a few things that jump out at me.
The first quote, if I'm reading this correctly, is about $12,000 USD. That's a good price for the full installation of a 7.1.4 surround sound system with a projector. But, the projector is a real turd in the mix and if I were to spend money up front, I would start with a good projector, a decent screen, and good audio with proper wiring.
If your space hasn't been wired yet, then consider that if you have to open up drywall to run wiring, you might as well run 1.25 inch or larger flexible conduit, then run HDMI cables through the conduit.
The cables certainly aren't rated for 18Gb/s UHD content, but the projector isn't UHD capable either.
The first quote, while it offers a lot, and at a fairly good price from the looks of things, has a VERY poor projector quoted. Not sure the US equivalent, but it's very entry level.
The second quote doesn't even list the model of projector you are getting. That's like saying "CAR: Chevrolet" - Wait? Am I getting a Spark or a Corvette? Epson makes projectors from a few hundred to several thousand dollars.
The third quote uses what appears to be the EU version of the Epson 3100 or 3700 model.
Only the 6300 is really a decent entry level models, but I would get the BenQ HT2050A over either of them in a heartbeat.
It's great that you got three quotes, but I am concerned with any company that pushes B&W in-wall/ceiling speakers when someone is doing a first time setup on something of a budget. In my experience, the cheaper B&W speakers sound no better than what others offer for less than half the price.
The projectors you are looking at are okay, but if I were putting together a good dedicated space, I would want a good mid-level model or better. I would want something that is 4K capable. This means the Epson 4010 or the Epson 5050 models would be on my list. If I had to save some money, the BenQ 3550 would be a decent place to go, but contrast isn't as good as the Epson models. JVC if I could afford it.
The hardest part in all of this is the wiring. If you are on a budget, but can afford to spend more later, but want to get going, then get the wiring in place. Hopefully you can look online to price out what a 500 foot roll, or about 150m of 14/4 wiring will cost you. Then you can compare pricing to what they are charging. I think a 100% markup on cable is typical, but more is crazy. In the USA, 250 feet of 14/4 is $123 from Monoprice...
https://www.monoprice.com/product?p_id=2817
About $250 for 500 feet of the stuff.
The first quote bugs me because you are spending a LOT of money on things which can wait until later and make the room seem cool, without necessarily making dramatic improvements. Cheap screen, cheap cabling, a fair bit on power conditioning (which may matter a lot), a lot of money on acoustical treatments which may not be of good quality, $2,500 on speakers, then a $1,500 receiver to run it. All of it paired with a $850 projector. WHAT? One of these figures is WAY off from the rest.
I would be looking at the Epson 7400/9400 model projector for that space if I wanted excellent results...
https://www.projectorcentral.com/Epson_Europe-EH-TW9400.htm
I would put in 1.25" (or larger) conduit and only ONE HDMI cable. I would run 14/4 cabling to all speaker locations. I would avoid acoustical treatment at the start unless my budget really allowed for it and I knew it was benefiting my room a good deal. I would use floor standing mains/center, and on wall surrounds. I would use lesser expensive effects speakers and the best subwoofer I could get. I would paint the room DARK DARK DARK!!! Dark walls, dark ceiling, dark carpet. Pair it with good lighting in the room.
I'm not sure what your budget is, or what the price differential is between the US and where you are buying from.
The one number that jumps out at me is that installation labor for the first project (the only one with a number) is listed as being under $400. That's a completely insane number. I guess if you have sub $10/hr labor, it may be right, but that number indicates that you will get installers that don't know how to install things properly.
I might go out and buy my own equipment, then pay someone to run the wiring (in-wall) and hook a few things up as I would be concerned about the quality of the craftmanship of others in this situation.
