I define marginal fee cost as the number of bytes required to add that UTXO as an input to a TX multiplied by the satoshi/byte rate of the blocks being found.
So for a normal p2pkh UTXO, this would currently be roughly 180 bytes (number of bytes this UTXO would take up in a TX as an input) * 200 satoshi/byte, or 36000 satoshi. So the answer would be however many UTXOs exist that are 36000 satoshi or below for p2pkh. Essentially, I want to know how many UTXOs are currently in the UTXO set that would not be worth redeeming should the fees be above a certain satoshi/byte.
I would like this data at 100 satoshi/byte, 200 satoshi/byte, 300 satoshi/byte, 500 satoshi/byte and 1000 satoshi/byte.