An advantage of posting your rate on your website is that it adds straightforwardness to the process. One of the things that drives me nuts is complexity in financial agreements. For me there are two modes of operation: 1. Its a lump sum fee, and no matter what I will finish the job for that fee.
2. I will charge you $X/hr, and you will pay me for every hour that I work no matter how many that is.
Total transparency about your hourly rates is a positive because clients understand that this is just your rate, and you are not screwing them or giving someone else a better deal. For bonus points, you can even round off to a nice even number like say $100/hr, or $200/hr.