That is not true. In years past, money helped a lot, but letters and phone calls have always had some level of effectiveness. Dollar for dollar, a letter signed by a constituent is more effective than an expensive lobbiest (it helps that the cost of letters are disproportionately low - unfortunately, it takes a lot of letters to be effective).

There are a lot of "grass roots" lobbying going on for nearly free based on emails, web pages, and social media. In fact, it is so effective that many lobbiests have adopted "grass roots" mechanisms to lobby - see "astroturfing" http://en.wikipedia.org/wiki/Astroturfing.