The higher the remaining quantity of a coins, the more accurate the break even price can be calculated.  If the remaining amount is too small, the break even price is no longer meaningful.  Assuming you only have one thousandth of a coin, you would have to sell it for an astronomically high price to reach break even.  So if someone has a very low residual value, they would have to sell it for a few trillion euros to get to 0.    

Since it would make no sense to display this, the software instead shows "too low".