How to sell ad space for a local coupon shopper?

I started a local coupon shopper for small businesses, but I am having a hard time selling ad space. My costs are much lower than any of my competitors, however I'm stuck on how to attract local businesses. I have a website and I have over 5,000 flyers printed and even sample magazines to show potential businesses. The monthly publication is free, and we have a circulation of 140,000 copies in metro Atlanta and have a version for each county - that's 20,000 copies in each county. My competitors charge $1200 for a quarter page ad where I only charge $150.

Does anybody have advice on how I can sell more ad space?

I am no expert in marketing but as a consumer if the price for one product or service is way lower than a related product or service then I feel that there is something wrong with the item or service being offered. I think scam and move on. Maybe you just need to move to a more competitive pricing structure that is lower than your competition but not too low that it seems like somethings wrong.

Just my 2 cents worth

you must prove that you have a high readership. They don't care how many copies you distribute, they care about who reads it and what the demographics are (probably coupon saving moms & so forth)....change your communication up. Sell by sharing the number of readers you have & what their demographics are.