IIRC that offer has been going for a couple of years now. Although it's undoubtedly fine value, I can't imagine anyone wanting to buy two... it's not a "his'n' hers" style of e-bike.
They've been kicking around since before the "China Import Duty" was imposed. That's a long time for those batteries to be sitting idle.
If David wants to clear them, why doesn't he just offer them at £850 a piece (which is all he's getting anyway)?