Cost of more credits

I have the ultra annual subscription so I can’t “upgrade to a higher plan.” That option would be a significantly cheaper way of buying additional credits as opposed to buying top off credits (even with the discount on the latter).

It’s in poor form to require an ultra subscriber who wants additional credits to purchase them solely as top off credits (at a premium over what others are able to get them for buy upgrading to a higher plan). Why would you offer lower tier subscribers a lower cost per credit purchase price than what your “VIP” subscribers are able to purchase them at?