I found my Raymond for 6,000,000 bells (like 6-7 tbt) and 35 NMT, on this site, in October. I don’t know if the person who sold me him had checked the conversion rates at all because they were an older user but it seemed like they hadn’t been online for a while, so.. idk. You kinda have to find the right person.
Other people on here really value TBT highly, you can buy pretty much anything in the game with it. Like genuine paintings being sold for 10 TBT and so on. You could also use the TBT Market for something outside of Animal Crossing, people used to buy Flight Rising currency f.e.
If you're looking for IGBs (in-game bells), this probably isn't the best site- most transactions here are for TBT. I've heard Nookazon can be a good place to sell for bells... but my understanding is the review/feedback system there isn't as good, and it has more than it's fair share of shady users (plenty of good ones, too, of course, but it only takes a few bad apples to spoil the bunch, y'know?)