I don't want to bring up the exchange rate any further on that thread, so I'll continue here.
Someday, ig bells may reach a point where IG bells can no longer be traded for TBT bells, so the only way to make a lot of TBT is by selling collectibles. But then again, the absurdly rich members on this site don't want to share their TBT bells with anyone, as nobody wants to get in-game bells.
So it's the fact that people don't want to share TBT bells anymore. Not the fact that they don't want in-game bells.