You say "it definitely didn't just get cheaper to mine", which sounds obviously true, but in a way I'm not sure it is. If the price of gold decreases by $200/oz

You say "it definitely didn't just get cheaper to mine", which sounds obviously true, but in a way I'm not sure it is. If the price of gold decreases by $200/oz, that probably makes a bunch of mines unprofitable, leading them to close down (or at least pause) their operations. Which in a way would mean that (on average) gold got "cheaper to mine". And it seems to me that the Bitcoin mining market works basically the same in that sense.