Every optics (primary weapons only) cost 30 Certs, why is different for sidearms? I mean, 30 Certs are ok, but 100 Certs HELL NO, it's expansive! When you buy a 1000 Certs gun and you also need 100 Certs for a damn optic + 100 Certs for an hypothetical silencer + 100 Certs for a flashlight... it's painful! Plus, the optic you buy couldn't even fit your play-style, so you need to waste other 100 Certs for another one. Could you reduce the cost to 30 Certs ?
Well...when sights got released for sidearms people were so happy about it they settled for literally any pricetag. It's been left at that ever since.
I suppose it follows the logic that a sight for one's sidearm is a more specialized piece of equipment, which would reasonably cost more than something literally everyone buys at least one of. Wouldn't be against lowering the cost though.