Handling and charging for support with clients
I manage 80 sites of varying sizes.  Small brochure to large scale eCommerce.

I have a way of charging for support and assessing a monthly fee for this time and it's currently "adequate" but I don't know if there's an industry standard for this.  How do other people assess the support needs and cost for a client.

The other part of this question is about standard support and priority support.  Is it unethical or sleazy to have two support options.  One with X number of hours for a response time and charge 50% more for half of X number of hours for a response time.  
Handling and charging for support with clients
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I manage 80 sites of varying sizes.  Small brochure to large scale eCommerce.

I have a way of charging for support and assessing a monthly fee for this time and it's currently "adequate" but I don't know if there's an industry standard for this.  How do other people assess the support needs and cost for a client.

The other part of this question is about standard support and priority support.  Is it unethical or sleazy to have two support options.  One with X number of hours for a response time and charge 50% more for half of X number of hours for a response time.  