All these are around the same price. A set will be more than 1500 yen, but less than 2000. Not cheap, but worth it.
Top Tier:
Nick and Renee's -- This place is fantastic and the shakes are good too. It's a bit spendy, but I have not had a better hamburger anywhere. I've never had trouble parking.
Frank's Ride & Eat -- A close second to Nick & Renee's. Another amazing hamburger. I'd go more often if I could be sure there was parking.
Very Good Hamburgers:
Outback -- It's been a while, but I remember these as a solid quality hamburger. Don't eat too much of the Bloomin' Onions before it arrives.
Hard Rock Cafe -- Again, I haven't been there for a while, but like Outback, this was one of the first real hamburgers to appear in Osaka.
Kua'aina -- Hawaiian Hamburgers. These are serious burgers and I suspect people know them. They just make the list.
Going to try next:
Kohaku Burger Cafe: Not been there yet, but looks promising.
Tried and won't be back:
Shimauma Burger -- Small and not near as good as the others on the list. I left hungry for the same price as the other places.