To clarify with the rare items bit, say there are 500 merchants scattered all across Earth. Some are in the last city, some are hidden in the far reaches of the planet. I would say that only the hardest to find merchants, say 50 of them, would carry rare (not the rarest) items, but only say 1 or 2 items. By rare, I mean like a special version of an assault rifle that has some special upgrades that are medium/hard to find. Basically upgraded items that you can still create/find, but not crappy pistols or anything. A decent weapon or armour piece with a decent upgrade.. It has to be worth purchasing. The prices for such an item? A high price, but not so high that it would drive you to forget about it. Just within grasp if you play another couple of hours.. You never know, you may stumble across it on your quest to earn more money to buy the item.. Or not.