I used a guy (and his two-man crew) that did all the heavy work when I nearly doubled the size of my raised garden the previous year. I told him before we agreed on a price that I only wanted to specific things done, use only cypress and have it at least 2-3" thick everywhere. He estimated it would take 6 yds., but from past experience doing it myself, I knew it would take 9 yds. and told him so. I gave me a price based on 9 yds. When the crew finished the job, they had used one trailer-load of mulch, and I asked the guy driving the truck that pulled the trailer what was the capacity of the trailer. He said 6 yds. They never returned with more mulch and I thought to myself: "I have a feeling the depth is less than I stated I wanted". Now, a year later, I know that it was barely 1" in a lot of places, since I placed commercial plastic around the bases of a lot of my large trees, before mulching the landscape for the first time, to eliminate weeds growing there. That plastic was exposed within 6 months.
I never said anything, and I know I should have. My "kind" streak showed up rather than my "do what you said you would do" streak. He will never do another job for me. If he asks why, I will tell him. We have lots of landscape/lawn management folks here. Mississippi State University graduates dozens of landscape architect and golf coarse turf management folks each and every year, and there is always one or two that remain in Starkville.
Though my wife doesn't want me doing the mulch any more, I will more than likely just do it myself, a yd. or two at a time.