The gemara (Kid 31) illustrates the extent to which one must go to fulfill kibud av with a story. There was a non-Jew named Dama ben Nesina whose father owned a precious gem. The Chachamim wanted to buy the stone for the ephod, but when they came to make the deal Dama turned them away. The keys to the safe were under his sleeping father's pillow and he would not wake his father. Hashem rewarded Dama for this act of kibud and the next year a parah adumah was born in his herd. When the Chachamim came to buy the parah, Dama told them that he knows they would pay whatever price he would demand, but he would ask them only for what he lost in profit from not being able to sell them his precious gem.
1) Of all the rewards Hashem could have given Dama, why was it specifically a parah adumah which he was given?
2) Why does the gemara go into such detail extoling Dama's virtues, telling us that he knows the Chachamim would pay any price but he wouldn't demand it. Do Chazal need to lay it on so thick?
The Kotzker (the same vort is quoted from others as well) explained that when Dama ben Nesina did this act of kibud av there was a tremendous kitrug in shamayin against Klal Yisrael. Here this non-Jew was willing to sacrifice a fortune for the sake of not disturbing his father -- where is our sacrifice for mitzvos?!
Hashem therefore caused a parah adumah to be born into Dama's herd. Kibud av is the ultimate mitzvah sichlis -- it makes sense even to a non-Jew. Even Eisav understood and fulfilled kibud av! (See Maharal in Ch Aggados). Parah adumah is at the opposite end of the spectrum -- it is the quintessential chok, a mitzvah that is incomprehensible. Dama was willing to give up a fortune to fulfill a mitzvah that made sense to him. A tremendous zechus, but Hashem set the stage for the Chachamim to top it. As Dama himself admitted, they were prepared to pay any price for a mitzvah that made no sense to anyone.
(Parenthetically, we pasken that it is the parent who must bear the cost of kibud av, not the child. In other words if your father needs a new shirt, it's kibud av to get him the clothes he needs, but you can put it on his credit card. Whey then is the Dama story a good example of the mitzvah? He was under no obligation to suffer a loss of his money for the sake of kibud?
Ran gives two answers: 1) there is a difference between kavod, which you don't have to suffer a loss for [assuming the parent can pay], and causing pain to a parent, like waking them from sleep; 2) Dama was only giving up potential profit, not suffering a loss of capital.)