Just feel sorry for them -- they are unenlightened! There was a day when I thought clothes, expensive carriers, fancy beds and such were all a little silly for dogs. Then I got a yorkie -- my how things change!
The people making fun probably think nothing of buying a $300-$400 purse or a pair of shoes for almost as much, fancy cars and the like. We all find things to spend our money on that make us happy. Being a dog person makes us happy and whatever we do to make our pups feel special and well cared for is returned a hundred times over in puppy love. Try saying that about a pair of shoes!
BTW -- your car seat and doggy dental weren't even splurges! They are just taking good care of your dogs. Most breeds don't have the dental problem our yorkies do. Many can get by without them, but not yorkies! And a cr seat is just a safe investment for both of you. Wonder how many accidents are caused from people allowing their pets loose in a vehicle. I still cringe when I see dogs riding in the backs of pickups!