Just a reminder that I am compiling the top 32 lists for Columbus in the post below, as far as I know this is the only place (so far) that you'll find them together in text format. You can obviously Youtube search "YCS Columbus" and browse around yourself, but I myself like having the text version all in one convenient location, since it's gonna take the Konami site forever and a half to put them up :)
It seems that Maxx C has spiked in popularity at Columbus, with Plant decks incorporating 2 or 3 in the main deck. Maxx C is pretty much the legal version of Royal Oppression. Sure it doesn't stop the monster, but at least you're getting something out of it and potentially plus'ing so that you can swing the momentum back to you. I remember early in the format when this card was only like $8-10.
Looking on eBay, the average Completed listing is $30 with a few outliers. If you wanted to buy one now, the cheapest Buy-It-Now is $37. Currently both Troll&Toad and ARG are buying them at 22 for 1st ed, and 21 for Unl ed. I would expect this value to increase over the next few days. Undoubtedly people will be wanting them since Plants dominated Columbus, and with them being Secret they're hard to obtain. There are only 20 listings for the card on eBay at the moment. I predict that they'll be ~$45 by the time the Wave 2 tins come out next week. My reasoning is that people will be able to get their cheap Solemn Warnings then, and be closer to building the deck that topped, and thus Maxx C will be in more demand. As more people want to play Plants, this card's viability keeps going up, so demand goes up, etc etc. It's also very safe from getting reprinted since the set is still fairly new. I'm glad I picked up my third a few weeks ago!