99 agility accounts are expensive because of high ban while botting and pain in the ass while making by hand, Can go easily for $100-200 I think if unregistered.
If the accounts are unregistered they can be sold without needing much vouches
I would say least $20 for first accounts
$25 for the second account
$15 for the third account
$40-50 for the fourth account
Just my opinion, could get more too.