We got quoted $6500 to install ours...
Installation will vary depending on the difficulty of siting and what needs to be done.
You can probably save yourself some money if you want by being your own general.
For example:
Buy everything from an online place like generators direct
Get the precast pad option (easiest) or get someone to build the pad
What about fuel? If propane, your propane company can come and hook it up. You will need a minimum tank Size for each model. With my 22K, needed 250 gallon min
Hire electrician to wire the electrical
Consult first on siting because a lot of codes apply such as distance from any opening to your house including basement vents. Electric codes, propane codes, etc etc.
I paid $5200 for the generator and switch and everything
Prob $1200 for additional propane tank (rented) and hookup line to generator. Needs a big line so also new regulator.
Can't remember on electrical but prob $1000 or so
Some to a contractor to build a retaining wall to put precast pad one.
I think 8K was the total.
Variable speed models are nice because they can reduce RPM when not under heavy load which reduces noise and fuel consumption as well as better lifespan,
My dad did the same thing on the East Coast with an all in one generator place and it was more like $12k (Same model)