Trade-in Value For Full Piggy Bank

I think that there should be some kind of trade- in value for a full piggy bank. The piggy bank is full of our earned gold bars, and those players who are unable or unwilling to pay $2.99 should have another option to obtain them.  I have been playing this game for a little over a year, and I have seen very many pop-up ads to remind me that my piggy bank is full, only to find out that I have to pay to receive those gold bars.  If players could trade in their full piggy bank for boosters, at least they could benefit from all of their hard work.