What does it trade for these days? A good friend of mine who does not trade is asking me to trade one of his T20s for a tasty sour of some sort. He asked about Duck Duck Gooze specifically and a few other Cantillon one-offs. Thanks!
Haven't traded one or traded for one, but I'd think your friend wouldn't have any trouble at all getting something very good for it. Here's your best option: put up a FT: T20 ISO: ________ and find out.
I think your friend should just bring it into the brewery and share it with the regulars. That would earn some major beer karma.
Consult the wale list (shameless plug). It'll trade for things lower than it on the list, but probably not for things higher than it although you may find someone generous. To your question specifically, you can definitely land a DDG with T20. As far as the one-off/rare Cantillons go, you can probably land: JCN Crianza Blabaer maybe 50N4E But you're unlikely to get offers for the likes of DQ, Loerik, etc.
I would think, if anything, its value has gone up, with some people wanting it for T25 side-by-sides. This value has nothing to do with how it's drinking at this point, of course. It's really not so good any more.
I would likely do that if it were my bottle but it's really not my bottle to share. We both just had it on draft which was tasting much better than the bottle I had a few months back.
A strong dark sour that's well past its prime - I'd maybe trade for it just to keep it around as as decoration or something. The last few times I've had it it wasn't worth drinking.