I don't buy used tack either
. The only exception to that rule for me is bits because they generally don't require as much specialized care as leather. If a bit hangs in a tack room or lays in a box for 10 years, just rinse off the dust and it's good as new (provided it hasn't rusted beyond all repair). Leather though, I don't trust other folk to take care of it the same way I do so it's just easier for me to buy new.
HOWEVER, I don't buy tack with bling and silver and jewels and full tooling either. It's all very utilitarian, but that's why I can get good quality at an affordable price.
I've always been of a mind that when people see me riding my horse they should think "Dang, that's a nice horse" instead of "Dang, that's a flashy bridle" LOL.