Main question was not about duping gold, by all means limit how much gold you can bring from Classic Era to TBC (once u commit to first go to Classic Era) - 1k sure, reason for such feature is not gold but experience content at your own speed.
How it should work:
- Xfer your char to Classic Era (not copy but xfer)
- Finish all content u want in classic Era with your char
- Xfer (not copy) your char to TBC server (same realm) with limits what you can bring with you (gold, items, mats etc etc…).
Yes it could be paid service, but it would give you as player to enjoy any Era of the game until u are done with it.
And who knows, maybe I want to check out Warlock, and I want to start it from Classic Era and then move to TBC? So now what? if I’m new players and start in Classic Era after I’m done and killed KT, then I need to make new warlock on TBC server and level it again?