Something rings so true about this. Treat your customers like you actually like and trust them. Give them more reasons to give you money, and they'll gladly do it (special editions, re-releases, etc).
The author could take advantage of his customers' desire to hand over money by offering something in return, satisfying his need to engage in trade rather than charity. Everyone would be happy. Customers get more stuff, he makes more money, and no one feels like they're getting shafted.
I have little reason to suspect that being in the cloth-map business is going to be any more worthwhile in the long term than being in the IP business.
It's obviously not going to be a huge source of income, but if it a few percent of revenue or something, depending on the amount of work necessary to make it happen, it might be worthwhile.
Example: I've been a fan of the Warcraft universe and lore, and I own a pile of Warcraft merchandise: action figures, posters, t-shirts, and collector's editions of every Blizzard has made a collector's edition for (I don't even play the new WotLK, but I like having the collector's editions for the art and soundtracks).
If he's got some customers are as rabid about his games as I am about the Warcraft universe, he could at least increase his revenue by a few points, even if it's just simple stuff like cloth maps, t-shirts, and soundtracks included with a Collector's edition of a game.
I don't think that's unreasonable. Obviously it's not going to overtake the rest of his business, but it could be an additional source of revenue, and even advertising (T-shirts are walking billboards), people talking about the "awesome" inclusions in collector's editions. Stuff like that.
The author could take advantage of his customers' desire to hand over money by offering something in return, satisfying his need to engage in trade rather than charity. Everyone would be happy. Customers get more stuff, he makes more money, and no one feels like they're getting shafted.