It's funny how Thailand failed to realize that people want to pay money to stay in Thailand longer time. But they don't want to pay too much money. So why don't they make it a "subscription". As long as you pay you can stay one more month...
I think in principle that readily could charge a few hundred US dollar per year... The big problem is all the paperwork. So make it a 6 months extension in the country for cash, if you are in "good standing".
I don't know how it is today but the chinese visas at the embassies you used to pay when you pick up the passport with the stamp in, and you paid according to what visa they gave you.
Nowadays they say you need to use an agent, and I guess these may not be refundable and maybe even the visa fee?