You can't explain it. Simple as that. Well I guess you can explain, but usually not in a way anyone else can understand. My brother called recently and was rather proud of himself, and figured I should be too. He'd just bought a $9 pair of Skullcandies. He was very impressed with the sound as it was much better than the ones he usually got from the Dollar Store. I told him that it was great for him and hoped he enjoyed them knowing they almost certainly sounded terrible.
Now how do I explain to him, in a way he'd understand, that it was a good idea for me to spend $270 on an Ibasso D10 and $200 on a pair of Grado sr325i's? It's not possible! Even if you say "Yeah, but you spend your money on (insert useless wanted item here)" people will always think their wants make sense and yours don't. I don't understand why my wife has 40 pairs of shoes and I never will, and nothing she said would convince me otherwise. But she gives me room for my obsession and I give her room for hers. I think, unless you both share an interest, that it can't get better than that.