According to Odaily, as Bitcoin (BTC) falls below $55,000, only five mining machines continue to be profitable. These include the Antminer S21 Hydro, Antminer S21, Avalon A1466I, Antminer S19 XP Hydro, and Antminer S19 XP. The shutdown prices for these machines are $39,581, $43,292, $48,240, $51,456, and $53,187 respectively.

The profitability of a mining machine is determined by the cost of electricity and the price of the cryptocurrency being mined. When the price of the cryptocurrency falls below a certain point, it becomes unprofitable to continue mining. This is known as the 'shutdown price'.

The recent drop in the price of Bitcoin has led to a decrease in the profitability of many mining machines. However, the five machines mentioned above have managed to remain profitable despite the drop in price. This is due to their high efficiency and low electricity consumption.

It is important to note that the profitability of mining machines can change rapidly due to fluctuations in the price of Bitcoin. Therefore, miners need to constantly monitor the market and adjust their operations accordingly.