In Everquest, the process is different.

Transfers (/testcopy) from a main server to the Test Server is almost unlimited (once every 8 hours).

I don't remember (any) information for my bazaar mule account.
So my play accounts had basically 50,000 platinum between them.
I transferred 49.96K (and Ualaa's Manastone) to test (via /testcopy), traded those to account 2 and did another /testcopy, then traded to account 3 for a final /testcopy.
I repeated that twice a day for about a week.

On test, transferred to the permanent characters, who are leveling there.
So the /testcopy characters could freely be overwritten, and have their valuables returned...

Items that go for a massive amount on a live server, don't cost all that much on test.
For the most part, high end gear is from a live server and can be copied freely to test and repeatedly.
So people essentially give the gear away, for a few hundred to maybe 1k platinum for most things on the bazaar.
I've frequently seen people giving away tradeable max level epic quality items in tradechat.
And it's also very common for nodrop (Bind on Pickup) gear to be advertised in zone/general chat, for anyone who wants to come and loot it.

Platinum is almost unlimited, in that you can copy it freely.
And you can copy items that sell well, also freely.
My friend liked to do factions, so he's farming assorted Orc Belts on a live server (and getting Rebby Rat Whiskers, etc)... then /testcopy them to Test, so they can be reused every day, without needing to farm them for weeks and weeks.

It's not really an exploit, that's just how test works.

Eventually you reach a point where you can infinitely afford everything that you'd buy from an NPC.
Mercenaries cost so much platinum, per 15 minutes... which is fairly trivial, if you're doing things appropriate to your level... and especially trivial, with unlimited platinum (over time)...
After that, platinum has little meaning.