Steve,
was on a business seminar some years back (must pull out the notes sometime) and the consultant giving it told us that if you increase your prices by 5% you can afford to lose about 17% of your customers. Dont know if it is totally true and I’ve not tried it but I do feel I need to weed out some time wasters.
what i found works quite well is actually to offer some of the work you dont really want to someone who is starting off and keen. they will be happy for the work, you will build up a nice bunch of people that then can help you out when you need it
an example might be someone without a studio, you give them the work you dont really want and they recipricate by hireing your studio for work that they need it for