Cost/Benefit thumbnail sketch:
USSR 2.0 drones about 50k each (average of decoys to live drones that attempted to return to the Belarus Oblast arbitrarily set at $50k as likely many more decoys than drones were used and there is a cost difference between them)
4 drones shot at successfully, $2.2 million per missile. Lets assume only 1 shot per hit and maybe 1 miss for Murphy's sake. $11M lets say $10m just in case some ground based non-missile solution was used (it does not seem any Patriots actually launched although some batteries likely were activated - I stand to be corrected).
But that should not be the cost used in calculating the benefit. It is likely unknowable unless the shooter is within mark 1 eye ball range in daylight with an experienced drone hunter as to precisely what the target is. That is kinda the point of (longer range) decoys sent to map/test air defence coverage, response times and threat magnitude.
The real cost is an opportunity cost. 'What If' any of those 4 shot down had successfully engaged targets with live warheads and were triaged as harmless / left to hit their target; potentially a hospital, apartment block, headquarters, military airfield (although I have not seen any indication yet of a Geran cluster munition variant - something I hope Ukraine is working on it they do not have one already), refinery or other high value target whose value might easily be in the 10's of millions not including loss of life costs to the state, society and the individuals family.
With that in mind the 'Fox 2 ' (AIM-9 Sidewinder - Infared homing) decision is an easy one, even the far more expensive 'Fox 3' (AIM-120 AMRAAM - Radar homing) decision. The unforgiving never tiring bitey things circling your head at night sleep depriving (cue the NFB Blackfly cartoon) WW4/CW2 factor is the absolute shallowness of the "do not dive here / no lifeguard (US) on duty" NATO magazine depth; the ENTIRE collective Wests completely inexcusable scataphillic ostrich proclivities that STILL have prevented adequate contracts being issued, budgets increased, doctrines and war plans revised/updated/trained, and re-election fear tendencies squashed.
The West is so far behind the 8 ball you need a 4-16x50 S&B scope to read it. With luck we might beat a surplus CUCV's downhill 0-60 time in months not seconds.