Have you used any calculators from an installer like Tesla or frequented solar owners forums to read about actual experiences?

It is extremely dependent on the state you reside, how much electric you use & the energy company you have as incentives vary.

Tesla, in NY on PSEG LI for example- $9K would get you 8kW solar w/o storage $20K would get you 12kW solar + some storage, installation and tax included

In New York State with Fed, state and utility incentives it's like 4 years.

Hmmm. No. The payback is 20 years, which is the length of the panel life, and the limit on time the utilities have to pay you for the energy. After that, they get the energy from you for free.

You are making sweeping negative statements without specifying where in your experience this is the case. 20 year pay back would have to be a state with super low electric prices and absolutely zero incentives.

Please specify where this is the case and why, per your math.

Fed is 22% tax rebate, NY state is $5k incentive.. and power in the state ranges in the 20-30c/kWh range.. so pretty expensive power with pretty good incentive.

Yes, continue the explanation with your math, including the part where you don't actually get that rebate; as part of the solar program financing, you have to hand that rebate over to the bank to pay the finance fees, which is factored into the financing. Otherwise the monthly payments go up, and you end up paying more per month than you generate energy. I was in RI and RI rates and program is similar to NY's.