I agree with West Mains in the sense that I wouldn't pay five dollars for a map.
I'm not as talented when it comes to mapping as you are Indrah, but I can still make a dozen or so decent maps within an hours worth of time. I am assuming that with your skills you can probably do the same amount of better quality maps in that same span of time, and by charging five bucks a map, just based on this observation not knowing how long it would actually take you to make a dozen maps of your caliber, you'd basically be evaluating your time as worth 65 bucks an hour, that's not including charging extra for puzzles or anything special and the like.
If you did do the "bundle pack" idea where you just make a set of maps and throw them up on say the RM store or something and sell them like the music/graphic packs, then I would think the best way to do that would be to have themed map packs. What I mean is like having one pack be full of just lush forest maps, another pack of snowy maps, another of desert maps, ect., because I don't think there are many people that would spend 20+ dollars on a pack of say a dozen maps just to end up only being able to utilize one or two, and then having to edit and change those one or two maps even still to fit with the other maps the person has made.
I actually think Wes Mains has a good idea in regards to writing a book about the art of good mapping. I know you've released things on the forums about mapping in the past, but make a book of sorts that's really in-depth, involving theories behind why you would wanna do things a certain way, why x is better than y, how to do Y when all you know is X, ect., whatever your book would entail. People love buying instructional books, so that would probably be the best way to go while still valuing yourself at a high price. I wouldn't spend 25 bucks for a collection of things I could learn to do on my own for free, but I would spend 25 bucks on a book that showed me how to do it right and the theories and things behind doing it right. That's just me though, there are people out there that are so lazy they would be willing to pay you to make their game for them, so take what I say with a grain of salt.
I guess bottom line is I think anyone valuing themselves over $6/hour something simple like mapping is holding themselves too high. I don't mean to offend by saying that though, just can't think of a better way to say it haha.
Make a guidebook about mapping though and I'd pay 10+ dollars for it in a heartbeat if it was detailed enough. Plus if you do a guide you don't run the risk of getting those people that want your services, then once you made the product they would be like, "Nah, I don't like them, I'm not paying.". I mean if people are smart enough with their money, they wouldn't pay in advanced and hope that they're getting their monies worth, they'd pay at time of delivery once they've had a chance to look it over.