In 2036 the block reward for mining is 0.39 BTC, what would theoretically happen, if mining cost are bigger than the reward?

By 2036 99% of all Bitcoin will be mined and the mining reward for it will be 0.39 BTC.

Don't get me wrong, I am a Bitcoin bull, but what would theoretically happen if the BTC gets another "low" in the future, so that the mining cost exceed the block reward?

Do people just stop mining then?

I came to that as a shower thought and I kinda confuses me to think of it. Just 0.39 BTC as a reward, it sounds so small. With the bear market around now, I think of future bear markets and if this can affect miners then.

Bullruns can be great, but bear markets hurts.

Maybe I worry too much and 1.69M per Bitcoin eoy 2036 is real and nobody worries about electricity cost for mining then.