That'll work for some purposes, but not others. If you want an item that can be bought and not sold, f'rinstance, or a whole bunch of them, it won't do you any good.
No, for this, you need to either not use shops in the normal way at all, or use a script to edit shop programming.
Like, changing line 309 in scene_shop from
$game_party.gain_gold(@number_window.number * (@item.price / 2))
to
$game_party.gain_gold(@number_window.number * (@item.price / 20))
for example.
Oh, and you'll probably also want to change 249 from
@number_window.set(@item, max, @item.price / 2)
to
@number_window.set(@item, max, @item.price / 20)
unless you want some very confused players...