It’s so bad that my fiancée has some bras that say she’s a B cup and others that says she’s a D cup. In order to go bra shopping, you have to actually try them on to find out if they fit.
If I had to try on underwear to see if they fit, I might not bother with underwear at all!
Trying to buy bras for my wife has been an eye opening experience.
One thing that I haven’t seen mentioned here yet is the Wild West of standards once you get to big cup sizes. Apparently DD is the same as E, DDD is an F, and I’ve even seen a DDDD, which would be a G. Depending on cuts, brands, and styles, her size can go from a DD to an I.
Not to mention these things are like $100 for a “cheap” one. The amount of engineering it has to take to design that shit is probably a few years of grad school.