Where are you staying in LA ? If your hotel is near the venue, remember the venue is not near LAX. So, are you talking about transportation costs from LAX to your hotel ? Rent a car for $20 a day. Car rental at LAX is inexpensive compared to other places.
To be honest we travel a lot for cheer and I don't find much difference in LA. I'm traveling to NCA in a few days and I've found hotel and transportation costs are about the same as in LA. But, LA is a big place and if you're not familiar with the area, I'm sure it can be difficult to navigate and make arrangements.
Is it possible that LA just does things a little different than some other cities. For example in LA you need a car to get around. There's not much public transportation you would want to use. I have not been to Atlanta so I can't compare the two cities. You will be happy to learn LA has lots of cheap hamburgers. But, you might need to drive to get to them.