Mr. Jury is spot on. If you're thinking this is going to be a long term venture and these footwear are going to be the next big thing, don't be frugal with your logo mark.
There are many design agencies that specialize in branding, which is where your direction should be. Aim for a reputable agency that is near your location. Why? If you'd like consultation and immediate influence on the progress of the design process it's necessary to be readily accessible. (You'll find that phone conversations, texts, emails, faxes, Skype, etc. are nice tools, but face to face direct contact is wayyyyyy better and highly responsive for both parties.)
Think of it this way: How much money is the NikeTM Swoosh worth? The SwingmanTM logo? Or the UnderArmourTM logo mark?
I'd say $500-$1000 for a great logo is REALY inexpensive and could have the potential to rake x-times the amount in return. If it brands well it will sell well--all retail possibilities besides the shoe.
Best advice. Do some serious research into possible design agencies that specialize in branding within a few hundred miles of your location. Give them a cold call and see if you can set up a meet and greet. Get to know them and their message before a choice is made. After all, this is a process and you may need there assistance from here on out, for as long as the product is in existence.