I have some comments on this, since I know you're all dying to hear what a non-mapper/modeler thinks.
Obviously I'm a big fan of custom maps. Specifically I'm a big fan of a couple of custom mappers, including Youme, which I think he's aware of. That doesn't mean I agree with him on this, though. At the time that you agreed to sign the contract you believed it was fair, and I'm sure you were quite happy with the $5500 you've received for something you'd probably have done for free. I know early on in Hoodoo you weren't expecting it to become an official map, anyway. So $5500 is only NOT fair because of the amount received by modelers.
Complaining about the amount of money you receive based on the amount someone else receives later under different conditions makes me think a lot about professional athletes, which isn't a good thing. It also makes me think of people that buy something only to have it go on sale the next day, and then complain about the price they paid. Obviously they felt the price they paid was fair or else they wouldn't have dished out for it at that time.
The big picture issue, obviously, is that customs maps don't make Valve money the same way items do. Sure, they increase sales slightly shortly after each update, but I'm guessing it doesn't even come close to the sales from Polycount items. My solution? Take money generated from keys and distribute it evenly between all mappers with an official map. The money is extra for Valve anyway, and it'd get people to stop complaining about key costs to some extent.
As for the idea that the community values items more than maps, I'd have to agree. There are some of us that value maps more, but I think much of the community is happy playing the same 4-5 map rotation on their favorite servers anyway. The items that they get can be used in any map and any game mode, which makes them "worth" more as well. Finally, they change gameplay, which is the biggest aspect. Certain maps have the ability to change gameplay, but mostly they just provide variations of situations that exist on other maps. Even when they have something groundbreaking it's just in one area and doesn't change the overall dynamic of the round. So based on all that, of course much of the community values new items more than new maps. It's a little unfortunate, but predictable. :/
My recommendation for the mappers: wait and see. Valve is obviously interested in taking care of all of you which is more than I'd say for other game companies. Complaining about it until you see how they handle it won't change anything other than people's opinions about why you map, which I know from chatting with some of you wouldn't be accurate.