I’m not saying you are wrong, but its: A) not necessarily a matter of expense, but one motivated at least in part by ideology (can’t let the union win) And B) mainly about perceptions. If people believe their job and possibly future employment opportunities are at risk, they are more likely to break. Scabs aren’t necessarily unskilled, they are just people who have decided the cash is more important than solidarity.
In an ideal world employers would realise a content, healthy, and properly compensated employee is better for the business and the economy in general. In reality they are going to keep cutting corners until the whole thing falls apart because line goes up.