Be careful where you buy Scotchguard.
I've seen prices vary for it by as much as £25.
When I do protection, which isn't very often, I use Fluoroseal by Prochem for carpets
and Aquaseal by the same company for suites.
Only ever protected one suite and I charged £45 for that.
For carpets it varies.
If it's for a single room say 4m x 4m I charge £3 a sqm.
If I'm going to be using most of it up in one house I charge £2 sqm.