Thinking a bit more, many Nintendo published titles tend to hold their values, as a good chunk go OOP and are never seen from again. Doesn't mean they are worth 2k monies, but they arn't 4 buck titles always either.
I havn't played Mario's Picross, but the controls are pretty much the same, save the addition of the stylus 'marking'. I really liked it's controls, but I know a few others who were older Picross fiends who didn't. I'd hold on to your copy until you stumble into another one thats open (if you care) because I've been on the hunt for that for a friend for a few months now with no luck.
It had a short run at the early on in the DS's lifespan, it had very good versions of Monopoly and Battleship and Atari's license to those games went away when Hasbro clamped down soon afterwords.
Battleship has been re-released, along with a few others in the Hasbro 'Friday Game Night' compliation, but that was the only way to get Monopoly on the DS. There is a new Monopoly DS game coming out, but that isn't getting release until next month ( I think). Once that release hits, if the version doesn't suck, the price of Monopoly/... might come down.