Slotting the struts is the more correct way to do it, and it's not abnormal for them to need that kind of work.
You are just paying the labor to get it done. A standard alignment at my work is 80 bucks, then can be another 40-60 per axle if we need to take the time and slot struts or do something else.
You aren't getting raped, you are just paying for what needed to be done.