Is the figure 24.7 wrong?
Yes, it's wrong. 24.7A @ 12VDC is a lot different from 24.7A @ 240VAC. Think of it as the difference between the power contained in water gently flowing through a babbling brook versus the same volume of water shooting out of a fire hose. You can't use the brook as your power source in order to pressurize the fire hose even if the volume of water is the same.
It is best to convert it to kilowatt-hours first and then to amps at the lower voltage. This is what I did in the math I showed you.
Would it be too long for the payback period either 77 pcs 120W or 36 pcs 210W for the 25.2KWH AC loading?
That depends on a lot of factors, such as if you consider other benefits besides monetary in terms of "payback". E.g. independence, self-sufficiency, fault tolerance, saving the planet, sticking it to the man, not having to run grid power to a remote site, inflation/hyperinflation, ability to outlive catastrophic social collapse, etc. If you're just trying to save a few bucks, then yeah, it's probably not worth it for that kind of load to replace perfectly good grid power with solar power unless you're getting every possible rebate and incentive. Your money would probably be much better spent making your load much more efficient. Then at that point, it might be worth thinking about going solar again.
If you describe your load, maybe we can offer suggestions on how to make it more efficient so that you could power it with fewer panels.