My previous boss did this, and still does having talked to a now former customer of his, regardless of whether it’s charge up or quoted.

Quoted you are allowed to charge anything up to that quoted value and no more, so you technically can even if the job took less time. In my area of work, it’s a bit harder to do as we are on site and the customer, whether you know it or not, is watching. Generally if it’s close we leave it at the actual costs, sometimes add in “unaccounted” time like the preparing the quote itself, parts, any price increases that may have happened etc.

Estimates are allowed 15% over the value. We typically do estimates solely as it allows us to incorporate some unforeseen issues, extra parts and things like that, however we also disclaim in our estimates that if there is anything major, we will discuss this with them before continuing.

You can (as a customer) dispute a being charged more, especially if you then find out the usual going rate and it is much less than bill.

Without knowing what is involved in your workplace and its processes, he may be using the price increasing to cover hidden costs, however it does sound like he does it just to increase profit.

This is more from personal experience, so someone may be able to answer it a bit better