Paul's Hamburgers are amazing! My dad used to buy burgers from there when he was a teenager, and he says that until this day, they are exactly the same. The burger with the lot is absolutely delicious, and the milkshakes are amazing, too. Definitely worth the over-full feeling afterwards! Best to skip a meal before eating one of their burgers - especially if you plan on picking up some yummy pineapple crush or a delicious milkshake. Best value for money, and I gladly travel across Sydney to enjoy one of their burger. What is also really great, is that the place is always packed, so you know the food is good. We usually take our food down to the park or the beach, because Paul's is generally overflowing with people - definitely worth the wait, though! They are not open all days, so you should call before just showing up, or you could always order over the phone and pick the food up, which mean you completely bypass waiting in line, altogether ;)
The cost I list is the approximate cost for a works burger with chips and a milkshake.

Approximate cost: $18