I don't know man... I stopped trading turnips a long ass time ago when I think I was around 25,000,000 in the bank? I just check prices for the thread. I still have nearly 70 million in the bank right now (just checked, 68.8 million exactly. ARRG! I forgot to use ABD yesterday so my bonus streak is gone!). Making money is like... butt-easy in this game. I sell all my golden roses every 3 days for 79K bells, sell all my produce every 3 days for a little over 100K, and all my fruit whenever they come back for 111K, too.
Like, if I randomly buy a Nook Miles Ticket and find myself on like "tarantula island" or "fin island" I'll catch as many bugs as I possibly can and drop everything else in my inventory. Then I'll just hoard them in my storage until the next time Flick or CJ makes a trip to the island.
That's about where I'm at. I make 100,000-200,000 bells minimum every time I get on to play (every couple days). Any time I spend a bunch of bells, I just make them right back. At least I can take a break from selling turnips. I think the only thing left for me to do at this point is to get into
the Happy Home DLC.