Quite often, some of the inexpensive scales on Ebay will be very good for not much money. It requires a known good scale to compare them to however. For instance, I bought one of those Postal Scales to weigh my guns, etc on here at home. As it turns out, it is always Dead Nuts when weighing certified test weights.
In my opinion, a Pocket Scale should be inexpensive enough so that when it crumps it won't be painful to throw away and inexpensive enough to, perhaps, withstand the purchase of two or three to get a reliable one.