I charge the listed rate for almost everything. If something is going to be a lot of administrative work or tie me up for a real long time, then I'll ask the band to suggest something extra as a bonus, and the band has always offered enough that it seemed fair to me.
It's more expensive and disruptive to go to an outside studio, so I have to have all that extra expense covered (travel, food, telephone bill, bla bla bla), and the time lost getting to the gig and coming home needs to be paid for, but the billed daily rate is the same.
Once the extras are added in, it can be as much as $2000 additional, which is really only sustainable if the session is long enough that the daily rate economy will offset it. For a short session, it's not usually worth it to work elsewhere unless a lot of money is saved some other way.
If you want to set a flat rate, just do it. Tell the client it'll be $X for X number of days including travel and everything. I've done that too, depending on the session.
sa at electricalaudio dot com
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