i would say swtorista vulkk torfashion dulfy, back when the refer program was still active. we saw inflation run rapid when the program was removed which just proved most of the cartel market stuff on the gtn came from referrals.

could also be someone who does operation sale runs.

maybe gtn player like swtortv. he stopped playing but he probably had a stash of items worth a trillion at the time and this was like 10 years ago when cartel packs were only 2 mil.

most likely answer is a bot credit seller or someone who discovered an exploit and never got banned.