So I've thought about this a bit. Assume there are a fixed number of transactions per block (N), but a greater number of potential transactions that people wou

So I've thought about this a bit. Assume there are a fixed number of transactions per block (N), but a greater number of potential transactions that people would like to do. Also assume that there is a maximum percentage (of transaction amount) that people will be willing to pay as a fee (F). Then I think the transaction fee should tend to F * average amount of Nth largest potential transaction in a block window. The cost of mining a block ought to tend to just less than the average block payout (reward + fees). When the reward disappears, this will happen as miners shut down due to not being able to make a profit and the mining difficulty decreases. Only the most efficient miners will survive. I think this means a few big miners, rather than many small miners, as big miners are almost certainly more efficient.