Yikes - I just checked the local five guys (we have not gone in a few years) - a small cheeseburger is $9.49. The 'regular' is 11.69. Little fries are $5.19. A coke is $2.99. Total for a regular / small fries / coke with tax is $21.06.
That is just way out of line! (suburban Washington DC - not close in....)
BTW, not sure where you live but a double cheeseburger at McDs is $3.19 around us....
Not doing fast food is good for health - both your own and your wallet's!