Out of interest, I tracked down an article from this year, talking about ref salaries - significantly higher than the last one I'd read (which I also tracked down, and was 13 years old!). Ignore their maths though, it's utterly horrible, but they seem to know the pre-match salaries.
http://tsmsportz.com/money/rugby-referees-salaries/
So a RWC ref gets £1500 per (RWC) match; TJs get (£750)
An international ref gets £1000 per (international) match; TJs get (£375)
Premiership/ SRugby refs get £350-375 per match; (TJs unknown, but the same ratio gives £130-180).
So a top, top ref could earn (10x£1000)+(30x£360)=£21,000 in match fees, realistically a little more if they head south for SuperRugby and Quad-Nations.
Meanwhile, a club-grade ref would earn (40x£360)=£14,400 p.a.
Same article suggests that top-level refs can earn a (presumably performance related) "extra" of 2.5X their match fee per match, but only seem to suggest that at RWC level, but if we assume the same across the board, then that salary raises up to £70,000; (£50,000 for club-grade - who will also spend plenty of time running the line instead, so significantly less) realistically I think that assumption holds for international rugby, but probably a lesser bonus at club level.
Bear in mind that even most of the elite refs hold down day-jobs as well, and all of the club-level ref.s do. Owens on the after-dinner speaking circuit, Barnes still works as a solicitor etc.
The article also demonstrates horrendous maths, by suggesting that top-level refs can earn £320,000; which would require the match-fee + full "extras" for refereeing 46 RWC matches per year.... which seems unrealistic somehow.
They also think that $250 per match gives an annual salary of $60,000; requiring 240 matches per year...