Pros vs cons of DIY solar?

I'm looking to install a somewhat customized off-grid-style (battery storage) system. My roof can support 5-6kW of panels. I have found a local installer who will take care of just the panels portion, wired to my specifications, for about $20k (pre-tax-rebate). On the other hand, my estimate of ordering panels (altestore, including delivery and 25% spares ~$2.5k), racking ($1k), renting a lift ($1k - its a steep roof), wire, conduit, and permitting and inspections is something like $6k.

This feels like a huge delta to me - enough to pay for the entire remainder of the system including the batteries. However, I live in an area (upstate NY) where building permits are required and there are lots of code requirements. Although I think I understand these and can meet them, I'm feeling that's the most daunting part. I'm also a bit concerned about working the steep roof, and I don't have any experienced assistance available. I managed to put up all the roof decking myself, but hired someone to put on the sheet metal.

I assume this group is likely biased toward the DIY approach, but do you think I should take this on? Are there costs or difficulties I'm likely overlooking for the DIY approach? Has anyone tried DIY and concluded they wished they hadn't?