It's a completely business model, though. Slice just provides online ordering for existing pizzerias. The marginal cost of each pizza sold is very low, so they don't have to make a lot off of each pizza to eventually be successful if they have high enough volume.
Sliceline was doing things with high operational costs like repackaging and delivering pizzas, so their marginal costs for each pizza were very high. That means they have to make a lot off of each individual pizza no matter how high their volume gets.
https://play.google.com/store/apps/details?id=com.slicelife....
Slice is here in New York and I've been to their office and I know many of the programmers who work there, so I know they are surprisingly successful.