If you were to pay for this service, what would you be willing to pay?

I have started a side business (in addition to my day job) as a press release writer. I've gotten lots of clients and am wondering what I should be charging for my servce. What would you pay someone to write a good, solid, SEO favorable press release? It takes a lot of time and effort for me and I put out a good product. What price would be fair on a per press release basis? THANK YOU!