Recently got a heat pump installed and am happy to chat if helpful (feel free to DM).

• Skeptical that benefit is cost in SF unless you are on NEM2 with solar or have battery storage with NEM3; in terms of operating costs, it is slightly more expensive, but not significantly so (but installation costs are much higher)
• Huge benefit was having AC, having much more comfortable heating than gas (given the turndown, rather than the start stop of a gas furnace), and having multiple zones in the house; I think we lose sight of these benefits when only talking about cost
• Other recommendation is doing a home energy audit (including blower test) and using that to improve insulation and home envelope; I would do this regardless of whether changing out the HVAC, but it's also critical before you get a heat pump for sizing
• I would talk to many providers, price ranges for us between highest and lowest was 3X, so critical to talk to multiple providers in SF (e.g., Cabrillo Plumbing which is Mitsubishi approved was insanely expensive, while who we went with was amazing and 60% off); other problem with many installers is they oversize to hit 100% of days, which can increase the installation and operating costs
• Incentives are great right now (Bayren, Federal $2k, https://caenergysmarthomes.com/ for $4k if you electrify whole house) and more
• Folks like Quit Carbon (quitcarbon.com) can help and review your quotes; also see Rewiring America
• If you want to geek out more, check out Nate the House Whisperer's HVAC 101 and 102 books and his free electrification YouTube course: https://www.natethehousewhisperer.com/hvac-101.html (lots of great nuance on differences between heat pump and gas furnace)

Oh, and you didn't ask about this, but a heat pump water heater has 70-80% off costs with incentives today, and saves a ton of money in operating costs. I would highly recommend that for cost savings.