This issue will always exist.
On Arma it was the mentality of caring about your kit not your life - if I am going to die/get taken hostage I would rather just 180 and maybe get a kill or two rather than just give it up. A "similar" menality will appear on FiveM because the dynamics are similar (A life RP server with a functioning economy)
You need to make kit cheaper and people will give it up in the name of RP is ultimately what I can say through my experience on life servers. As a cop (on arma) i would not mind being taken hostage because my gear meant nothing so it was an enjoyable encounter. As a rebel on there, I would rather taken a fight I would 100% lose because it is more fun than throwing an expensive kit down the drain. The same sort of scenario will always occur on FiveM (although in a different style due to the rules you must follow).
End of the day where there is an economy which makes things hard to get, people will be less happy to just hand it over. If you were to make pistols cost 10k right now, there would be an signficant increase in true RPers who will improve their RP because ultimately their gear means a lot less to them, whilst at the same time there would be a signficant increase in idiots running around with pistols - you see the obvious problem.
Gear is expensive = Winning > RP
Gear is cheap = Too many idiots who would then go the other way and not care about their life because gear is cheap.
Ultimately, weapons should be somewhat attainable whilst not costing the price of a half decent car (IDK much about FiveM but at one point I thought pistols would sell for over 100k - that is the price of a half decent car)
You see the problem - when permanent equipment (cars) cost the same as temporary equipment you could lose in an instance, that temporary equipment becomes what you value, not the RP story you are meant to be persuing.