This would be my guess. 300k a stack for something you farm one at a time is abysmal.
Think about 18 incursion bots who get 300 stacks of wings/feathers/tusks and instead of npcing them turn in 700 coalition assignments
I'm still not seeing the scale as relevant, tbh. If you cut the cooldown to 10 min and leave the tag cap at 15, you get a whopping 5 * 11400 = 57k bayld (5.7 h-p bayld) every 2.5 hours from dullahan armor (and the rest are worth less). Someone making every single turnin 24/7 all month would walk away with 1642 h-p bayld. Expand it to 18 chars and you have a little over 2 ergon's worth of extra bayld in the market.
That's also assuming an ultra aggressive 24/7 incursion farm that isn't actioned and cares enough to add imprim dumping and doesn't lose time to being in incursion when cooldown maxes. I don't see it moving the needle, probably wouldn't even match the additional demand from easier prereqs.