I absolutely agree with your response @Jacob.
The problem with offering varying degrees of services is that, if you are a true professional, you will know what service the customer needs and offer nothing less! You know what needs to be done to get the job right, and offer no other option. Otherwise, you can’t take pride in your work, and your client will not be happy with the result. That is unacceptable. Know what you need to do, know what will make the client happy and offer that service without compromise.
Upselling, or selling add-on services is a different thing altogether. If you are offering window cleaning, there are very little options beyond inside or outside and frequency.
Some add-ons could be track cleaning, screen cleaning, frame cleaning, pressure washing, gutter cleaning, etc.
You can offer those (or more) services and even give a discount for each add-on.
But, your core service (window cleaning) shouldn’t have grades. It’s either done right or not at all.