What the best way and economical to get updates about the prices and offers from local dealers?
I want to cover 58 areas local dealers/retailers from my city.
Ok, I think I understand what you are looking to do. The situation is that you have a bunch of businesses in your area and you want to bring all their pricing data together in one place to be analyzed or displayed.
So the first big hurdle is collecting that data.
Options for collecting the pricing data on their products:
A web app to collect this data could be written quickly with Ruby on Rails, and hosted freely on heroku.com. Or you could try to use Google docs / forms / spreadsheets to do it.
But overall this is a difficult problem to solve, and no one has found a good way to solve it. Startups / websites that want to have the price of groceries at all the locations so you can buy products at the cheapest places still do this by manually sending someone into the store to log it.
Website that do gas pricing at all the gas stations around the city have crowd sourced it and allow people to submit prices in via a mobile device. If you could some how get your audience for this data excited about entering it, or turn it into a game then you might have better luck collecting it.