It is expensive, but it isn't usually that expensive. OTOH, for some used piece of crap raft, I suppose it could be. What's your life worth? Flares are pretty worthless and could be left out of the survival kit without any significant impact on survivability, but the cylinder is the big problem.

It is not easy to detach or empty a charged cylinder from a conventionally packed aviation life raft without unpacking and repacking the raft. That IS expensive. I can think of only one where it might be moderately easy and it is an expensive raft, which few ferry pilots would purchase because they usually go for cheap and light weight.

That doesn't have to be so, but most ferry pilots are way to cheap to have one custom packed to allow it to be done easily. I have also made suggestions for a feature that would allow the CO2 to be vented and recharged without repacking, but not a single raft manufacturer has bothered with it. Too expensive for too small a market it seems. Sooner or later someone will die and then something might happen.