The Gemara Kiddushin [31a] describes the case of Dama son of Netinah in Ashkelon, who turned down an offer to purchase a precious stone because the key to the chest where it was stored was under his father’s pillow. Two questions: 1) Wouldn’t the typical father be more upset by not being awoken for such a financial opportunity? 2) Doesn’t Halacha not require us to suffer financial loss for parents?
Possibly the answer lies in another story about the same Dama ben Netina that appears at the bottom of the page you quoted. In that story, he is consulting with the great men of Rome when his mother rips of his expensive clothing and spits in his face. He does not respond or embarass his mother. From this story we might learn two things. Obviously Dama ben Netina was wealthy and influential. It is possible that the wealth was accrued after the last story (his windfall from the Para Adumah). It is probable that he was wealthy all along, as he was trading in precious stones. Second, it is likely that his mother was suffering from some form of dementia. Could it be that the father as well would not have been able to appreciate the huge profit, or they were just so wealthy that Dama ben Netina felt the mitzvah was worth more. Certainly there is an element of "lifnim meshurat hadin" (going beyond the letter of the law) in this story, but it certainly shows the extent of thye care taken that Dama be Netina's parents should not be disturbed.