How much would it cost to neuter a 70-80lb dog

Yes, but weight and it is different for cats and dogs and gender....see below. I love them. Taken all my animals to them and my sister has now taken hers. CATS                             $89               $84    DOGS (by weight)        0 - 25lbs                        $171                $171 26 - 50lbs                       $189       $189 51 - 80lbs                 $208                $208 81 - 100lbs                    $224                 $224 This is from last year, may have changed.

My dog was 45 lbs and it was about 140 I think.

I believe it does go by weight so your better off calling them. They also have specials sometimes. The website has info.