will there even be 15.5 million gold's worth of tickets bought?
That is not a problem, the gold prize depends on how many tickets were bought for the
last draw. So there's a guarantee no money can be created by the lottery, except the first prize but it has already been largely compensated by the ticket spendings.
Which means if people bet more on this one than for the previous, the prize will increase again. So far the lottery has put about 4,5 million gold out of the economy, so I'd say it works alright.