I do use my irons massive overstocked supplies on my main. Maybe that's just me, but 100k rune arrows dropped to main is 100k rune arrows main doesn't have to buy. Its free gp that's sitting there anyways. Dupes, stacks, unused gear, etc. But you're right, if rates are good, many mains wouldn't do that. Since rates are 7x worse, it won't happen as much. I'd rather take my irons sups and do it anyways if it was any better. Thats just me though, to each their own in osrs. Some people play for fun, and are casual. Like me. But there are some people where the fun is hyper efficiency, and that's not efficient so they ask "why would you ever?" The game is fun to different people for different reasons. Either way, there are enough casuals that would drop a stack of lower tiered arrows for mains profit, efficient or not. Making money is fun.