I dont understand how so many people are not getting it...

Helmet =/= body armor

If that round continued and there would be more Ts remaining then OP would've played it out with a helmet and without body armor. Meaning he receives aimpunch when he's getting shot in the body BUT if he theoretically was 60+hp and got glocked in the head from somewhere it would still result into a dink, OP receiving reduced damage and thus surviving.

The fact that his helmet stays on for the remainder of the round tells us exactly that, his helmet only gets removed after the next round starts which indicates a check at the beginning of the rounds that should be reprogrammed to prevent it from removing existing helmets even if body armor is down to 0 (resulting in a repurchase of $650, not $1000).

Or if this is actually intended then the helmet should be immediately removed after your body armor depletes. Now it just screams bug/programming oversight all over the place. Yes it's only $350 (which if you got down to 0 armor you don't desperately need) and yes you should never even let it get this far by replenishing it earlier BUT that doens't mean this is intended lol. It makes no sense that it's happening and should be fixed. The only risk you should be getting yourself into when not rebuying your armor at around 40 is that you potentially have to play the last part of the round without body armor, not that the game lets you play without armor, leaves your helmet intact but then removes it the round AFTER...