its hard enough to get people to use standards in development, much less rates.
i think in order for some kind of 'standard' to be accepted and adhearded to, developers would need some sort of governing body, like IEEE or OSI does for standards in networking, hardware, etc
without some governing body all the kids at scriptlance are always going to bid $5 for any job.
personally, I hope there is never a standard. I want people to bid $5 for some job. If anyone pays someone $5 for a script that is worth well in excess of hundreds, well, you get what you pay for.
free market, keeps prices down. its up to business owners to invest in quality products and make intelligent descisions.
do you need some governing body controlling how long your certification lasts or telling you you cant do something becasue you havent paid them this year?
to answer your question a little more directly, I believe a developer should charge fees based on their experience, how long a job will take, what expertise are involved, if the developer has a niche and is an expert (or just a kid), costs and overhead, etc. if you are going to take a contract or job to develop something, you owe it to the client and yourself to develop a plan before you quote someone a price. this plan should involve something similar the microsofts MSF model; microsoft solutions framework. the MSF consists of 4 main parts, all devided up into more specific task;
if a developer makes a good enough plan, the fees should be pretty clear once the MSF is complete.