If you look on Beltcheckers, there are a whole bunch of BJJ black belts that do not bother with registering with the IBJJF.
The IBJJF is not the only tournament org, although they are a large and well known one.
I have always suspected that it was your local promoting instructor, and possibly his immediate network superiors who put the shakedown on you for the affiliation cash.
Carlos Gracie Jr makes so much money on tournament fees and Gracie Barra affiliation fees, that it would be hard to imagine that he would spend the time on an extra $2K from an outside network.
But that does not mean the instructor and/or network that was offering you affiliation and who promoted you would not.
Or that they did not blame Carlos Gracie Jr / the IBJJF for why they were putting the bite on you.
I have seen networks and individual instructors try to put the financial bite on their students and affiliates many times.
However, I would remind the readers that some networks do not charge rank promotion fees, mine included.
And, one of the largest affiliations out there, BJJ Globetrotters, does not charge rank promotion fees either, and charges nothing to affiliate.
So, one can avoid the highly monetized pyramid business model networks in BJJ, or one can participate in them, and either way, still get belt ranks.
But, the situation you encountered, where a substantial financial bite was attempted after you were promoted to black belt, is a situation that does sometimes occur in some networks.
And, that is unfortunate.