At best you will only get 12mpg with a F-450/550 it doesn't matter if its a 7.3 or 6.0 if its a 6.4 look at 8mpg. It is cheaper to run a V-10 truck if your looking at new. I'am in the same boat all you can rent is a 3 yard bin or a 40 yard bin. There is a local disposal company that does have 10 yard bins and he isn't busy. The big problem is our landfill regulations you can't have a mixed bin of junk and dump it. Recycling is a big part of things here. Metal and wood are recycled along with drywall. So if you have a 10-12 yard bin full of mixed debris you have to sort it as you unload it. Nobody want to spend the money for separate bins for each item they have and nobody ever sorts what they put in a bin so its a mixed up mess. If I do garbage removal I have to load the truck so it comes off the truck in the right order I can't dump the load it has to be unloaded by hand. The benefit of having a rolloff for me would be easier to load I can drop a bin on the ground and load it instead of lifting heavy stuff into the truck. Also having a rolloff would mean I could do more jobs in one day if you know the stuff the person wants to haul away is one type of item only like yard debris etc. In todays economy what has killed my work is the " Do it Yourself " attitude to save money. More and more people are doing their own cleaning up they bought utility trailers or have a pickup truck and they do it themselves. Even on new construction or reno jobs the homeowners are doing the clean up to save money. I used to be busy and now I have nothing people are into saving every penny they can.