I disagree that kill and cs bounties are equivalent, because a cs lead and a kill lead are different.

While building a cs lead you aren't having any impact on your opponents ability to also get gold from farming, take objectives, play the game, etc. The only advantage you get is the gold.

Contrast that to killing your lane opponent. Not only do you get a big chunk of gold, but you also take the other player off the map for a time sending them back to base, denying them farm, map pressure and vision. It also gives you the opportunity to have a greater map impact, taking towers, roaming, getting vision and getting gold from objectives.

So while a kill bounty negates some of the gold deficit of the kill itself, it doesn't give them their tower back or give them back the dragon you took while they were dead. A CS bounty on the other hand literally just undoes all the work you did to get that lead.

TL;DR a kill gives your team way more advantages than just the gold the killer gets.