I charge hourly too. Since empty rooms are preferable to stretch in, it motivates the home owner to clear them before I get there...clocks ticking, right? Typicly I'll be at about $60 per hour, 80 if I have to cut a seam, add a second row of tack, replace transitions or anything else invasive.
I'll patch in with donor carpet for $50 per patch and $60 if have to transplant from a closet.
That being said, minimum for any repair is $120 and I'l never quote without an onsite inspection first. Besides, it's an open invitation to an upsell
fest on all the other services.