I get Dengie's alfalfa pellets instead, marginally cheaper and alfalfa is lucerne by any other name. I thnk they were about £10 a bag. Supply is drying up for now though because I suspect they are running out of last years crop.
I had a similar different brand Alfalfa brick to try recently. Two horses didn't like it and the third wolfed it down within about 5 minutes tops!
Bit expensive for the daily "extra" I'd hoped for whilst I had no turn out over winter but a nice treat for the one.