Well that all depends.
Anyone who charges you that much for install is raping you.
My install cost around 3k. That was only because I had to rent a ditch witch and dig up half my yard, plus cut into my driveway to get the gas line ran.
If you moved it yourself, poured your own pad, already had gas hookup and ran the pipe yourself, the electrical work should be less than 1k. It cost me 1200 to run electrical because I put a new fuse box in and it required quite a bit of conduit to get it where it needed to go.
Even IF, you had it delivered, gas ran to it with a meter installed, someone pour the pad, and someone to run electrical. 8k for all that is just plain dishonest, unless it comes with a backroom hand job.
After all the storms and outages, people have really started gouging the public to install these things, and it's just flat out theft.