Do you think you will be able to keep up on turning out enough product with those $20 price points? Dont get me wrong $20 is the perfect price for an impulse purchase at many shows. But if you want to average say $1,000 a day (to survive I have found this to be a good goal) over a 2 or 3 day show you're going to need to sell 100 to 150 pieces. And to sell a 100 pieces you're going to need at least 3 times that on the table.
Now I realize that my example might be crazy high for someone starting out (make it a goal), but divide that number out to whatever your goal is. Even if your goal is $300 a day you're still going to need to make a lot of product at those price points. Can your body hold up to that kind of labor? You need to be realistic with yourself and what you are capable of. Sitting out at a show takes a real toll on the body as well. Loading, unloading, standing in the sun for 12 hours, ect.
With all that said, I would suggest you have a variety of price points. you keep your low end stuff easy to turn out, and put some nicer pieces out where you can get more money for it. As long as the value is there people will buy whatever you put on the table. When I do shows I have things priced from $3 (not leather) up to $300 or $400 in the booth. Some people will buy the cheap $3 stuff, and others will buy the more expensive $400 stuff. I am a fairly young guy, but I will tell you selling at shows is not easy on the body. And when you're making the stuff it's even harder.
Like I said be realistic with your expectations. Figure out what you're going to do if your stuff sells too good. And figure out how often you want to work. Doing shows can provide a very lucrative lifestyle, but it doesn't come cheap.