It is not a one to one comparison, sco is significantly slower than the cashier (not sure about US but here Aldi/Lidl cashiers are madness). So i will just put a random number here but the ratio might be something lik 1:3 where 1 cashier would swap 3 SCOs. I still believe it is reducing staff and that is the whole point.

Our sco clusters have 6 stations each. you literally couldnt fit 18 more registers in our store let alone staff them. We have 8 registers and we’ve not once been able to fully staff those registers. at any given time we can find staff for maybe 4 of them.