Customer sacrifice is the gap between what you deliver and what your customers really want.
A gap of zero means you fully deliver everything they need, with the result that they are completely satisfied.
An infinite gap means you deliver nothing that customers want, and the chance of anyone becoming your customer is very small.
Customer sacrifice gaps may be deliberate or not. Either way, a sacrifice gap is an opportunity for competitors to better satisfy your customers and hence lure them away from you.
Example
A company selling lawn mowers offers no seat adjustment for customers of different height. They do not realize the problems this cause some customers. A competitor offers seat adjustment and hence gains market share.
A microphone is comfortable for most men, but rather large and heavy for some women. The manufacturer realizes this and introduce a lighter, smaller model, hence reducing the sacrifice that women have to make to use the heavier microphone.
A service company makes customers go through a long series of phone button pressing before they reach a customer representative. This saves money but annoys customers. Another company studies this and finds the economic point where the lower sacrifice of one button-press is accepted. They hence gain share by advertising this.