Earlier quoted context omitted.
In most contract work, expenses incurred by the contractor to fulfill the contract are almost always included in the contractor's invoice.
That was somewhat my experience. It was always the case where travel and lodging were required. Say, for attending depositions. But I did buy my own machines, and pay for electricity to run them. And I didn't invoice for maintaining stuff. So was that just my own naivete? And now that I think of it, buying better gear hurt me, in that it took less time to do stuff. But on the other hand, it allowed me to handle large…
OTOH, some customers are willing to pay for contractors' gear even if it would be used on other customers, for example, if they require you to use upgraded equipment instead of the equipment you already own.