engineer time costs and minimum time increments?

I suppose most standard support ops expected to be free and if we are talking about "extra mile" kind of work, like remote hands, custom sysadmin work on behalf of the customer etc... it is not really something that most professional users are too worried about. For all I care, it could be up to 50-100$ an hour in 15 minute increments, or slightly higher depending on location and type of hosting. It is not uncommon for biz clients to pay their own sysadmins up to 100$/hour or more and they should not be too worried about this, particularly considering that when one has a proficient sysadmin involved need of such service almost never arises.