No, the rider does not come out of the band's fee. It is an on-cost for the organiser. Most folk gig organisers make no more than the musicians and often less.

Of course that begs the question of whether Chum(whatever) are folk performers. Certainly they are not folksingers although conceivably they might be folksong singers. They are I think excellent performers descending from the folk idiom.

The question I perceive as apposite is whether a true socialist can justify ligging.