You do not have to pay $5000 dollars to use an MP3 file in your game. Not You anyways! To find out if you must pay to use an MP3 file in your software check out this site:
http://www.mp3licensing.com/help/developer.html
Here is a quote from that page describing who is excluded from having to pay license fees for playing back an MP3:
"Q - Do I need a license to distribute mp3/mp3PRO encoded content?"
The anser is yes, but read this.
"However, no license is needed for private, non-commercial activities (e.g., home-entertainment, receiving broadcasts and creating a personal music library), not generating revenue or other consideration of any kind or for entities with an annual gross revenue less than US$ 100 000.00"
Annual gross revenue of $100 000.00 - Your product will have to produce at least this amount of money per year befor you have to pay.
The developers of DBPro however have to pay on a revenue generated basis, because they use an MP3 player in DB.
They have payed that for you. And that is one of the real reasons people should be using DB. If you had to code you own MP3 player, you would be paying that license fee.