My guess is they are getting them on the cheap from providers who currently have an excess supply but will likely yank them back once their demand matches their supply. That or charge more.
Actually we can still buy /24s from providers in China who have way way too many allocations. Meanwhile we are limited to a mere /22 and we have to resort to registering multiple companies to qualify for more, which of course comes at significant cost.
If anyone has APNIC assigned IPs, honestly I am willing to BUY them from you. Let me know!