Firstly, I am not bragging.
Secondly, it's not about affordability, but about the risk in moving 800k baht to a 3rd World Country where I have no rights, and, by the way, neither do you, nor does every other retirement visa / extension holder. It's as good as a 12 month tourist visa, that's it.
Then, there is the convenience of not dealing with immigration.
Put all these together, and it's safer, more cost effective, and more convenient to use an agent, not to mention, the tax on remitted funds for new retirees.
I know you don't get it, and like the saying goes, I can explain it to you, even show you the math, but I can't understand it for you.