Sherlock was irritated and also a little disappointed when John innocently asked Henry Knight if he was rich. He didn't dwell on it for long but he had assumed that John would be above such a redundant question.
Obviously he was rich, the detective could give his doctor the first sixteen deductions that led him to form this conclusion if he wanted to hear them. Most had been formed before they'd even made it into the house!
But the thing that really got to him was that with this new data in mind, what would John think if he knew his background? Surely John would have already gathered that he'd come from a bit of money? Not that it mattered, it is the work that matters. Money was just something that allowed him the freedom to do what was most important. But what would the ex-army man say if he knew that the manor the Holmes boys grew up in was at least six times the size of Henry Knight's for a start?
He didn't have time to think about it for long before they were in the kitchen and moving forward with the case. He thought of it again once between cases and decided to bring it up with John who again said it was "all fine". He didn't show it, but a part of Sherlock relaxed at the reassurance.