The Second hand book Market

I feel that things are getting a bit stale in the second hand book market at the moment. I have been buying and selling books for 5 years now and I have dabbled in new books too and have found a sucessful niche market there. Howeve, I am finding that since selling online is getting more and more popular the prices seem to be plummeting. I am not sure whether this trend is likely to continue or whether it will eventually start to pick up again. I have a feeling that it will continue, which is why I am working on other projects to earn money as well.