A major difference is that the random brand merch you got was not worth much.
The rare skins in this loot box are valuable to some people:
With some skins currently in Jita for sale for 11B ISK, far more than the $10 spent to obtain one of these loot boxes. In fact, that’s worth close to $100 in PLEX.
Even a skin like this one EVE Tycoon sold cheapest for 2.7 billion ISK is already far exceeds the value of the amount of PLEX you can buy for $10, which is 200 PLEX worth about 1 billion ISK:
It’s as if you purchase $60 of clothes and they give you a random bag of goodies that sometimes contain another $500 of clothes. It’s gambling.