[kibwen]

The price of a single bot is amortized across thousands upon thousands of follows. If it costs a penny to have one bot issue one follow, and a single bot performs 5,000 follows, then that bot has earned $50. If Twitter were to buy follows for the market rate (one penny) then ban those accounts, it would drive the market rate for bots up to (using our hypothetical example) $50 per follow. (This is an oversimplified example, of course, but reducing the average number of follows that a given bot can perform would indeed have the effect of raising the market rate, though we can continue to argue over the magnitude; it's self-evident that if generating bots didn't have fixed cost overheads, then we'd see fewer bots with incredulously inhuman numbers of followed accounts.)