Considering the backs I’ve seen in the last few months this is minimal! Yeah, I would say about half of the time I usually need (you have half the hair!).
I’m now answering your question directly (and this has NO relationship to any other person’s estimate; only my own. I am not saying that any other person should be held to this estimate … just me!).
I would say about 35 hours maximum for the first clearance. 18 hours for the second clearance and 10 for the final one. That looks like 63 hours total; probably just a tad “high” as I prefer to give higher estimates. Your maximum expenditure with me would be less than $4,500. YIKES!
Bad news: you are not “done” growing in new hairs! The lower back can be 100% permanently removed (forever), but you will experience more hair growth in the seemingly clear areas … in most cases like yours, the is probably going to happen.