My city charges $300 just to pull a permit, and an electrician charges $100 just to show up. Then at minimum you'll need a new branch circuit, breaker, conduit, fittings, outdoor box, wire, interlock kit, and the outlet. And you better hope your breaker box has availability for a new branch and that it's recent enough for an interlock kit. If not, you'll need to replace the entire panel and all circuit breakers. And in my jurisdiction, grounding requirements had recently changed, and my local inspector required that I bring the grounding up to code in order to have any work approved.

It definitely would be thousands to get one of these installed in California. The electricians cost way over $100 per hour.

Also, a backflow cutoff is required by law, as are permits, inspections, etc.

San Jose has setback requirements, requires a concrete pad (for hardwired installations), and charges various fees:

https://www.sanjoseca.gov/home/showpublisheddocument?id=4499...

It wouldn't surprise me if you could get a deal on "new generator; free installation" though.

Installing an outlet yourself? Buy one for $10 or something, more if it's some special outlet, maybe spend an hour or two at most with the actual install.

Hire an electrician to install it for you? Between markups and labor, easily several hundred bucks at the very least. A thousand is entirely plausible.

Ignorance is expensive, knowing how things like electricity and plumbing work will save you money and help make life more fulfilling.

The parts alone to do it properly are several hundred dollars - the inlet box is around $60, 25 feet of 10/3 cable is $100 (obviously more for longer - wiring has gotten really expensive the past few years), circuit breaker $20, interlock kit is $150 (https://interlockkit.com/product/square-d-kit-k-5010-125-200...). Plus permit and inspection ($150 is the cheapest permit in my town). That's already $480 and you haven't even talked to the electrician yet.

If you get lucky and find an inexpensive electrician AND the inlet you want to install is located very close to the panel (minimal drilling, short wire, etc.), you can probably get it done for less than $1000, but probably not a whole lot less.