Price crashes do seem to be a disincentive for a 51% attack for owned miners. How much would the price tank versus the gain possible with an attack? The two don't seem interlinked strongly.
The price-tank disincentive is multiplied by the block reward size -- the lower the reward, the the less the miner would care. The price-tank disincentive also is attenuated by future equilibrium mining. If you make the first ASIC and don't attack, future manufacturers will pop up as mining becomes more profitable. If you tank the price, mining profits may become low, but you thwart competition.
Attack gains are not connected strongly to the above disincentives. Attack gains are higher the more often you can cycle the coin -- you can actually steal way more than the market cap of the coin theoretically by cycling exchanges / other mechanisms of payment. Then you start running your 51% attack and reverse hours, days, weeks of transactions.
I see your point that there is some disincentive for a 51% attack, but I'm not sure that's enough.
The price-tank disincentive is multiplied by the block reward size -- the lower the reward, the the less the miner would care. The price-tank disincentive also is attenuated by future equilibrium mining. If you make the first ASIC and don't attack, future manufacturers will pop up as mining becomes more profitable. If you tank the price, mining profits may become low, but you thwart competition.
Attack gains are not connected strongly to the above disincentives. Attack gains are higher the more often you can cycle the coin -- you can actually steal way more than the market cap of the coin theoretically by cycling exchanges / other mechanisms of payment. Then you start running your 51% attack and reverse hours, days, weeks of transactions.
I see your point that there is some disincentive for a 51% attack, but I'm not sure that's enough.