If you have too much money (1B cr) you don't earn any money on trading. However, you continue to earn experience for haggling. I just accidentally tested this when I was trying to warp back to my home sector after world trading.

I had picked up 999M cr to do something or other and had activated world trade without stopping to drop the money off on my planet. So I was running World Trade and not making any money. As soon as I noticed it, I stopped the script with a full load of equ. Fortunately, I was at a Class 3 (SBB) port and could simply sell my equ and buy fuel for transwarp. I turned on auto-haggle and docked. SWATH sold off my equ and gave me experience but did NOT empty my holds. It took a couple of tries before I noticed this. I was forced to jettison my equ in order to purchase fuel.

So the strategy can work like this: if you don't want to show evidence of your movements (besides docking logs) but want to increase your experience, just pick up a billion credits and world trade.

Or create a script that will repeatedly dock at the same port and fake-sell your product for 3-5 exp per turn.