My understanding of the Bitcoin ecosystem is that the task referred to as "mining" is actually the processing (confirming) of the Bitcoin transactions, and that the miner "finds" a coin when they find the accepted hash of a block of transactions.
Based on the information in other questions here, the mathematical difficulty of processing the transactions is expected to increase as more Bitcoins enter the ecosystem while at the same time the block reward is expected to halve at every 210,000 blocks.
The mathematical difficulty present in the mining process has of course a bearing on the cost of electricity and processing time of the hardware. On top of that the miners do have costs for paying for the warehouse or other location where the server farms are kept, besides indirect costs in things like depreciation of the hardware.
Currently we also have the situation that the USD value of BTC has been going down.
With this in mind I wanted to ask if there are any studies about the minimum USD value that Bitcoin should have in order to make mining profitable?