if the 'Show gaps' setting doesn't work, here is an alternative similar to the last suggestion:
Change measures to conditionally > 0 as follows
Sum(Costs) --> if( Sum(Costs)>0,Sum(Costs))
Sum(Sales) --> if( Sum(Sales)>0,Sum(Sales))
This will replace missing values that evaluate as zeroes with true missing values. See top as the default setting, bottom with the conditional values. Notice the change from 0 to - (null) and the effect it has on the line chart which i think is what you want
The data i used to create this was as follow. Note 2014 is missing in the 2nd load for Costs.