I've found Moira's approach useful, but as an option. Maybe:
Option 1: we apply the PU remotely and alone; walk IT through 1 workstation install/update; customer signs Moira's doc; 1 discussion with IT before signing the doc; we have one session after upgrade with IT person to walk through the acceptance checkoffs. Each additional discussion with IT: $300.
Option 2: Same as 1, except Upgrade and workstation upgrade done in 1 session with IT as shotgun. session scheduled 2+ days in advance. If customer cuts session short, we complete the operation. If customer requires us to come back to complete the session they cut short: $400.
Option 3. Same as Option 2, but with up to 3 additional calls included with the fee.
IMO the base price of Option 3 should be 3x the price of Option 2.
We've had very good luck with putting a price on half-baked discussions and haphazard scheduling and response actions by customer.