I just spent about $60 on these fellas, totally carved out the bottom of tcgplayer. I have about 30 non-foils and 5 foils. I love this card, hadn't seen it at all before I noticed its price spiking. big blue bodies are usually overcosted --> this has unique abilities and seems undercosted. Sleeper, indeed.
Wish I made my move on these sooner. I don't have any, but I'm thikning about paying 'retail' (right now, $8.50-$9.50 apiece) for one of these (it fits nicely with a landfall deck I have). Trade for these. These remind me of Boros Reckoner, which had multiple price spike while in standard.
All for now, happy investing!