I imagine carry prices will be lowest towards the very end of the expansion/content drought. I don’t buy boosts very often, the last time I bought an AOTC mount was at the end of WoD for the moose.
From what I remember the carry price steadily dropped as the content drought dragged on, I picked up my AOTC moose mount carry for 30k from a nearby local/friendly Mythic raid guild on the server.
The mount goes away when shadowlands ends. The gold cost depends on guild/person/“community” hiding as a guild. I don’t suggest you do it, easy way to get scammed.
If you’re on a popular server, it’ll go down faster then ever with many teams undercutting each other and actually having a chance to sell without all the huokan bots. Low pop servers, prices will be about the same or nobody would be selling.
Perky Pugs usually runs AotC until the next expansion’s patch. They use a lottery system, but towards the end of the expansion, they are usually funneling people through runs.
A lot depends on how long you are willing to wait.