This is a topic that I’ve always struggled with. There are so many things that factor into establishing prices. First off is the cost of your equipment. Even a lower end DSLR comes at a cost. Now start factoring in travel costs if you’re traveling to a customer or different location. As you begin to expand your collection of lenses and/or lighting your costs continue to rise.
From my perspective when charging for photography services you have to take into consideration not only the things mentioned above, you also need to factor in your skills. For anyone that has spent any time really diving into photography you know that there is much more to it than just picking up a camera and pressing a button.
On the other side of this conversation, just because you’re invested a lot of money in equipment doesn’t mean that you should expect your customer to bear all of the expense. You can have all of the latest and greatest equipment but if you’re not familiar with how to use it then it’s really of very little value. You owe it to your potential customers to be proficient with your equipment along with your photography techniques.