invaluable

You are a very strange creature by way of a friend!—always wanting me to play and sing before anybody and everybody! If my vanity had taken a musical turn, you would have been invaluable; but as it is, I would really rather not sit down before those who must be in the habit of hearing the very best performers.

The money I have received is so invaluable a sum that I have forborne as yet to pay it in, and am heartily sorry that I cannot better advance His Majesty's service.