Yikes, is that why Vux/Zed spiked from like 20k to 40k+? That's just selfish. It doesn't particularly affect me as I just wait until I get the ones I need from battling, but I feel for everyone who actually has to buy their stones.
I typically battle the S750 Kreludan Defender Robot - he's easy enough to one-shot with Lens Flare, even with a low-level battle pet, and provides Neocola tokens in addition to tan/red codestones. Not sure how his payout compares to others like the Koi warrior etc., but I've had decent, steady rewards from him.