How to prevent ppl from buying...

You can also put items up for 1 meso while holding the max amount in your inventory to prevent people from buying. I remember some guy did that with a pair of Face Stompers back when they were worth well over 100 mil (or something like that).

Wouldn't that be the opposite? Your scenario is having max mesos already with an item at 1 meso, while the question seems to be about how much mesos you need to have in order for a max meso item not to sell/in order to sell an item for max mesos.

I'm not entirely sure on this, but I would imagine you'd need more than the tax amount (3% of max mesos) in order for it not to sell. No experience on this whatsoever, so don't take my word on it, but that's just what makes sense to me.