I have a few comments about this, but to start out I'll say if you have above a 3.5, double major, and get a good GRE score you could probably get in somewhere.
With that said, the one thing you have that people currently applying don't have is time. You say things like assume A's and B's in math classes. The math classes you'd need to take you can get A's in if you could get B's with just more time studying. This should be priority 1A.
Priority 1B is to go to one of those in-state public schools that gives you the opportunity to do summer research. Get to know your professors the first day and throughout your time there, tell them you are interested in moving further, and ask them what you need to do to be successful. I am guessing they know of at least 1-2 students who have gone on to a graduate education in Economics from the school.
If you aren't willing to do these things on the outset, then maybe committing 5 years of your life post undergrad isn't worth it.