Depending on where the wires need to be run, it could easily be much less than $900, or more. The size of the wire is fairly expensive, and labor costs add up. Mine was a fairly short run, essentially across the garage, and the install was about $400 including permit. I had the electrician do some other things while there, and spend more than that, but I'm guessing that $400 was about the cost of the EVSE install. Lots of EVSE's out there in the $400-500 range for the hardware, excluding installation.
Most of the EVSE's are rated for outside use, but the install can be more expensive depending on what is needed. Using a plug means, generally, a larger circuit than if hard-wired. Code requires things that can be used continuously for more than a couple of hours to utilize the 80% rule...you can't use more than 80% of the power the line is rated for (so, say on a 32A unit, it must be run with at least a 40A circuit).