Cecil Sharp s collecting in the appalachians was necessary because the music was in danger of extinction,he on occassions rewarded his sources.
Dave Bulmers collecting of irish tunes was different,a considerable number of his tunes were collected from a session that occurred regularly [he acknowledges this in at least one of his books ].so the music was not in danger of dying out when he collected them,were his motives purely financial[Ido not know],possibly a mix of financial and a love of the music.
in my opinion a person who collects music, purely /mostly or partly for financial gain,should renumerate his sources in some form at the very least a drink for everyone..[after all without the musicians/ singers,there would be nothing to collect].
I hope the musicians that Bulmer and Sharpley[a solicitor who I believe was struck off] collected from, at the very least got a free drink.
There are other people who have published books of tunes in the last 30 years who I suspect have been guilty of not renumerating their sources in a morally correct way.