Let us examine this in a different way.

Any act of theft is an act that entails a molestation and a violation of an owner in respect to something he or she owns.  It is thus by definition, an immoral act.

Let us now consider the thief who steals $1.00 from individual A, $10 from individual B, and $100 from individual C.

In considering these varying acts of theft, we will quite naturally tend to view each act a little differently.  Normally, we will be inclined to say that the theft of $100 from individual C is a more serious and harmful act than the theft of $1.00 from individual A - and normally the thief as well will tend to value his theft of $100 more than he will value his theft of $1.00.

To us as observers, the act of theft may have no particular meaning or value one way or the other.  After all, it was not our $1.00 or $100, and nor were we the thief.  We ourselves neither gained nor lost anything as a result of the thief's act.

This is to exercise a value judgement, and falls into the area of utility, or subjective opinion. 

Each act of theft however, is in fact the same.  Each act is equally immoral in principle.