Be careful about the amount of cash you leave: “The popular belief still retains memory of this wild legend.. It was believed that Wayland Smith’s fee was sixpence, and that, unlike other workmen, he was offended if more was offered.”
From p219 of ‘Introductions and notes and illustrations to the novels..’ by Walter Scott. Vol 2, 1833.
This sounds reminiscent of hobs and fairies, who are also unimpressed by the wrong type of payment, and will stop being helpful after such mannerless behaviour.