I love how that we have a priority pass system in game, however I noticed that is not challenging as Peeps do no to buy it normally. No matter I feel it's free, people don't seem that interested in buying one, so my suggestion is to make the system more sensible to prices, this will make it more interesting and challenging. For example, if you set the price to $0, everyone will rush to get one and your priority queue would get busy, causing major dissatisfaction. In the other hand, higher prices means less people are willing to buy, hence you need to find the right balance to keep people happy and the system profitable.