I never buy plat (i.e. convert Krono to plat). I do sell plat at $9 per mil same rate as Krono, but I fully expect not to make many sales (maybe 1-2 sale a year) on it either. Why? Because plat is worthless in EQ and will continue to become worthless each passing day, so I fully spend all my plat on Krono and is the reason why I keep my rate so high on it at $8-9 per. As I do keep about 10 mill pp on hand usually, but am expending most of it into Krono. Which is why I have hit close to ~2500 aquired Krono by now since they went live. About 500 in the first month to close to 1500 the first year, they went live, since players were still trying to figure out the market worth on them.
It makes no sense to keep plat till there is something worth buying other than Krono for me. Till the EQ1 developers decide to fix the plat situation, I'll keep hoarding Krono.
Btw best place to farm plat - bazaar, all completely afk in offline trader mode. I've aquired 99% of my Krono through the bazaar, and I have about 500 on hand atm, still hoarding away.