Pretty cheap IMO. You would have to calculate the cost per hour of flight, should be at high 3 digits, and then add the expenditure of 2 small munitions (about $50k each).
So we could say that the cost is about $100k for destroying 2 Russian Navy patrol boats, which have a minimum of 2-3 crew each. I have read that the Black Sea fleet only has (had..) 6 such boats. That means a minimum of 4 people dead, and 1/3 of that ship type in the Black Sea fleet is gone for only $100k (which is also most probably funded by the US)
So, coming back at your initial question, the cost of using these drones to destroy these 2 patrol boats is essentially nothing in comparison to what they have managed to do
If you simplify the equation to the cost of missiles vs. destroyed targets yes, but if you consider that it is not a simple business excercise against the competitor but part of a bigger military activity then the assets,manpower and inteligence capability that used here missing from other places.
In that case you risk three of the last attack drone , valuable days of the crew and missiles for pointless targets, and during this time hundreds if not thousands of ukrainan troops die, and the capability of the ukrainan military decrease minut by minute.
Means attacking pointless targets decreasing the warfighting capability, and decrease the chance to win.
C'mon, Ukriane hasn't got any usable airforce, and the last air units used to attack patrol boats posing 0 danger to the troops and having 0 value in the conflict , at the same time the Russian aviation and artirelly pounding the defenseless ukrainan troops few hundred kms away?
