mwmiller The problem with this is that it can not be an option.
If we have $10/mo unlimited and pay per use what can end up happening is that everyone who is spending less than $10/mo is on pay per use and everyone spending more is on $10/mo -> we go bankrupt.
So we would need to completely change our business model to pay per use only. I personally like this idea (as it is fair and deals effectively with abuse) but it also presents a barrier to adoption. Only 10% of users told us they would prefer this option. Many users communicated that they would have anxiety to search knowing that every search costs them money which defeats the purpose of always avaialble search.
Looking forward to further thoughts.