If armor. You could buy a manequin put it on your apartment and place the items on it. Then put those items for sale.
Of course you need to open your apartment/house to strangers for that day. And someone could technically buy it before you login. (they must be psychics if they do so).
But you do not need to pay the tax and you could sell them all for 1 gil to your alt.

Otherwise:
- company chest.
- pester a friend.
or
- Sell at a higher than average price.
If gil.
- Have your alt sell something at a ridiculous price no one will buy and just give them the Gil that way. Of course you will lose the tax. Unless your alt has an apartment. Then just put some crappy armor for a ridiculous price on a manequin. You buy the item at the ridiculous price. And the alt gets the gil. I suspect that what happens when you see a 10,000,000 materia on the market.