Vassal exploitation?

Have anyone worked this out yet? To be honest I didn't even realize it was happening until my game came towards the end.

Basically any money you give to a vassal they give it back next turn.

SO...

Have a large some of florins approx 1 million (obviously a late game option).
Give them all to a side in turn for you to become their vassal.
Next turn you get the money back.
Now Give them all that money for all their regions.
Next turn you get all the money back because they are your vassal (and you should now have at least a good portion of their regions).

I don't think its a bug, just an annoying exploit. I mean, if you are their protectorate they should give you all their excess cash since they have no need for it!

Nice catch.

A fix might be to have the AI never take cash in exchange for becoming a vassal state, only gifts of regions, and then only if the military situation calls for it (player is very powerful, AI is very weak). Once they are a vassal state have them never accept cash for anything.