I have a friend who runs a small dev shop and has spent the past few months selling a simple Facebook app she built.
She charged a company around $10k for the app and got that rate by explaining how it would benefit their company. ie. Another form of interaction with customers, better brand recognition online, lead generation, etc etc. Apparently it took her about 2 weeks to build and she had to outsource some design work for ~$500. Assuming she worked 80 hours over the 2 weeks, she made roughly $120/hr.
Now, that's really good money, but that hourly number keeps increasing over time because she realized she could resell it to other companies by simply changing the branding and some design elements. She continues to sell it for $10k, but her investment each time is significantly less because the bulk of the work is done. It just costs her a few hours and the price of the design work.
In the past few months I think she's rebranded and sold it to 4 other companies. There are a bunch of factors into calculating the hourly rate for the project, but she essentially made $500/hr for that work.
Think about your work differently and what you offer, sell a product or solution - you won't get your rates up if you make your clients think of you as just another employee.