10x than what you wanted is a really huge difference. If the market goes down, imagine how much money you would lose. Also, if you sell it right away, with just the transaction fees, you lost some money already.
Methinks, you are confusing something here. Since almost all coins cost less than 1 Bitcoin per coin, and most of them cost substantially less than that (for example, 1 Bitcoin is worth around 2703000 Doges right now), you will almost always be buying hundreds or thousands of such coins. It seems that you refer to the price which is in the format of 0.00000x, but in this case even if you remove zeros, you will still buy or sell at the current market price.