As a comp, SunRun puts out detailed cost estimates for their residential systems each quarter[1]. Their average system cost was $5/watt, but with 50% of their installs having batteries. So for an 8Kw system (if you were buying outright) you should have gotten a quote of $40k with a "half-sized" battery. After US tax incentives, your cost should be <$30k including battery.

But yeah, if you're not in a region where they do a lot of installs, you won't get that price...

[1] "CreationCostMemo" tab in https://d1io3yog0oux5.cloudfront.net/_eb9fb58f3a5f81478f0536...