[leijurv]

Well it's a continuous process: today the fees make up maybe three percent of revenue, but that fluctuates as transaction space demand changes, and as the coinbase halves every few years.

But your point is good - miners are not really in a traditional supply/demand relationship with transactors, because block space is perfectly inelastic. There will be 7 slots per second (amortized), no matter what. Although... a petulant miner could artificially restrict this supply, by perhaps declaring that they'll never mine a transaction that pays less than X fee. This would only apply to the blocks that they mine, but the effect on overall supply could be nontrivial?