Rhubarb is over £10/kg. In a single year rhubarb plant should be able to produce a few kg of rhubarb.
At least that is what the internet tells me, I only got it a few months ago so the yield so far is zero. Oh and it keeps growing year after year and I plan to multiply it to grow even more. Tough I might buy a few more rather than go with just 1 so its a bit faster to get a decent sized patch of then. I also plan to make rhubarb wine and mead. Which is worth even more.
Herbs are worth quite a bit too, grow them to make my own herb salt mix for roast potatoes.
