To the OP...
Agree with much on what's been said here, particularly about pricing for different regions as you will get differing prices depending on where you are based.
You need to have a feel for how long the job will take you and then multiply that by your hourly rate and that's your price. Try not to drop down if the custie tries to chip you on price as you will then be earning under your hourly rate and why would you want to do that?
Personally I find this type of work harder than cleaning windows, therefore I have one hourly rate for windows and a higher hourly rate for gutters etc. If you can earn more doing maintenance window cleaning then it's not worth doing the gutters etc unless you are getting paid more for your time.
As someone has said you have spent money on your gear and therefore have the tools for the job so don't undersell yourself.
Hope this helps.
Mike