Price is but one element of your marketing mix. It's not unimportant, but don't give it more attention than it deserves. And don't confuse yourself by thinking that your competitors are charging anywhere near the price(s) the market will bear.
There are four (arguably more) P's in your marketing mix: Price, Product, Promotion and Placement.
Your "Product" isn't signs. It's the entire value that you create for customers, which includes the buying experience you provide and the results you help them achieve. So (more to Gino's point) focus on creating more value for your customers than your competitors can - and charge accordingly. Focus on becoming the best designer you possibly can. Understand that great design solves real business problems... and produces tangible results. Create something that customers will pay anything (within reason) to get.
If you follow the advice above, it will largely shape how you promote (and position - a 5th P) your product. That said, don't neglect promotion - even if you don't have alot of money. Learn how to use the social web effectively. Be creative. Show customers how creative you can be in promoting your business (and theirs) using the things your company is capable of making for them.
Finally, on the subject of placement, but related to price: I would add that many (most) people in this business start out by under-charging (hungry for orders, lack of confidence, lack of business knowledge) and rarely grow past that. I would recommend pricing everything as though you have the overhead of a real "bricks and mortar" business, so that you can easily afford to grow into one.
Good luck!