I wouldn't bother expanding there. It's not worth doing......or they have a lot of work they need to do on it first
I had about 6 trades turn up in a row asking for gold, I didn't send it. The last 7 balloons have asked for herbs.....one has just arrived now, let me see what it wants - herbs again. That's 8 in a row I am not sending. Herbs are a precious resource and needed a lot for trains/jelly maker so I am not giving them up for the balloon.
Regardless of what items it wants, the cost of doing the trade is no way reflected in the prizes being offered.
I am level 49 and each balloon requires 2000 to 2400 coins but the price that the balloon gives you for the items is less than half what you could sell in the market. So each balloon would cost me about 5000 coins.
I need to do 45 balloons for the big prize, so that will cost me 225,000 coins.
225,000 coins will get me the big prize of the bird bath and I have got two of those already. The other prizes are just decorations some of which you may already have. There is also a chance you could get 10 gems as a prize.
Now with 225,000 coins I reckon I could probably do about 20 train deliveries, perhaps more and can would earn me at least 100 gems.
So the balloon is not worth it. I would say only expand there if you have nothing else left to expand to.
I think the idea behind the balloon is good and could be fun fulfilling if it was worth doing and they could sort out the issue of repeated items being requested but for the coin investment of 225k to get 45 tickets, then the prize would need to be something of value.
I would say something like a pet which was not available anywhere else in the market. If that was a guaranteed reward, then that would be an incentive to complete all the trades.