Farming Bounty Question

How exactly does it work? Had a super passive lane and outfarmed my laner, got a 500 gold lead, hit tab and realized I had a 500 bounty on me. Around 650 gold lead, I had a 600, and that's just insane. If the enemy ADC took triumph, he's basically getting my entire farm lead negated for killing me once, not even counting what the enemy support gets for assist money. How is that even fair?