Justin has made some great suggestions. I would definitely check out the companies that he mentioned.
It's good to know up front that $30 for a song is actually not as expensive as you might think. In the past and even today, some royalty free music has cost as much as $1,000 to buy the rights for a film. Considering that, $30 is a steal!
That being said, I have gone to the Free Music Archive in the past to get free music for my commercials and documentaries: http://freemusicarchive.org/ However, it will take a bit of digging to find music that will work for you on a site like this, but nothing beats free!
An even better alternative is a website called Audio Jungle: http://audiojungle.net/. They have really high quality music and their prices are very reasonably priced (usually from $5 to $15). They are my typical go-to when I need a piece of music that I know will work for a commercial.
My last recommendation would be PremiumBeat.com: http://www.premiumbeat.com/royalty_free_music/ Though most of their songs cost around $30 (which you balked at earlier), they are good songs with great production value. You may find that $30 is a steal when it comes to some of their music!
Hope that helps!