Of course in this game, it's not only good value suppliers you need, you need good value right across you're entire marketing strategy to give you the most cost effective performance possible.
Things like SEO, Social Media marketing, Website development and so on, these things can cost a lot of money. To get the very best value, I suggest trying frelance sites. These types of sites are full of providers all trying their best to get your business, so that gives you the advantage and you shouldn't be afraid to use it.
Once you post a job on a feelance site, you'll start getting quotes in to take on your job. My advice, take those quotes as nothing more than a starting point and once you're happy with a provider of your choice, then start the squeeze to see how much you can get that quote down by. Remember, in that competitive environment the providers want your job, so you have the power to get the best possible deal for yourself and tu drive your budget further!