It is not expensive considering how much more energy it costs to mine 1BTC. Prices must go up otherwise no one will mine bitcoin.
its not that simple
if pools drop off.. block solves take a lil longer than the 10min average for a while... then the difficulty drops making it easier to mine. and also with less pools, means that the remaining pools get a bigger slice of the pie.
..
the reality is that pools have mining equipment hashing NON stop. even if their pool has not won that particular block.
because there are only ~144 blocks a day. thats only 144 slices.
imagine if there were 144 pools of all equal hash rate. they would only get (theoretically) 1 block each.
imagine if there were 72 pools they would only get (theoretically) 2 block each.
imagine if there were 36 pools they would only get (theoretically) 4 block each.
imagine if there were 18 pools they would only get (theoretically) 8 block each.
imagine if there were 9 pools they would only get (theoretically) 16 block each.
so lets say 36 pools now and it dropped to 9 pools
each pool went from 50btc a day to 200btc a day
so even if the price went from $10k to $5k the income would be from $500k but then upto $100k after pools dropped off..
..
there are many facets to the economics of mining. but be sure mining pools will not all give up 100%.. there will always be some that mine
but i simplified the basics of mining pool economics, though could have gone into further detail in regards to how the difficulty drop also affects income