Historically does the prices of the new machines goes down as the bitcoin price drops ?
Yes, they do, but not instantly like most people expect/hope, it can take months, and it will depend on the demand, unfortunately, many people overpay for mining gears, so they pay 7k for S19 today, and even if the profitability drops by 25%, they will still pay 7k, so this kind of "dumb demand" slows down the price drop.
Another factor would be the sellers refusing to sell at lower prices, they will hold for as much as they can, in hope of a difficulity drop or a rebound in the price so they can sell for higher prices.
These two factors plus a few others I might not be aware of, they keep the price from dropping, especially for brand new gears, used gears drop a lot faster in price.
I still recall that right after the halving when profitability dropped by 50% instantly, gear prices didn't flinch until weeks had passed, so I expect this time it will be the same, but profitability has to stay low long enough, if we rebound soon then gear prices will not drop.
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