I dunno, I'm kind of with the OP on this one. Seems pretty weird that I have to save several season's worth of my economy's whole output to buy a horse, or armor.
Of course, we can't be TOO logical about this - there is game balance to consider. After all, if it was all logic, my sovereign would walk up and say 'Yeah, I'll be taking that horse, and that armor... got any decent weapons? Sure, I'll take those too. What, payment? PAYMENT?!? I AM YOUR SOVEREIGN - YOU SHOULD BE HONORED TO SIMPLY HAVE ME IN YOUR SHOP! Now, wrap up my order before I lose my cool and burn your little shop down around your ears!'