I found one of these while out on my morning run the other day set up next to a lovely garden and house. Bags of broccoli raab - some just stems and some with the leaf - were on display for 100 yen each. (That's roughly $1.00 per bag, which is an excellent price given that the operation looked organic with it's big pile of compost in the distance, well-tended looking soil, and all the work that makes it a reality.) We had some for lunch with ginger and hot chillis over udon noodles, and I whipped some up to include in a rice-based potluck dish for that same evening.
I'm hoping to head over again today to pick some up for freezing. If things are as seasonal as folks imply, I am going to try to put some of this by now for future use. My hunch is that it would still be available, but perhaps not as readily nor as cheaply.