Anyone who bears an additional responsibility beyond playing their instrument (or singing) as required by the needs of the material deserves more. When you are a 5-piece at the $400-$500 level, the split is too difficult. All of us in my main band (in full electric configuration) are able to book gigs, but most fall to the leader, who also provides PA, and the trailer. The drummer and keys guys are video recordists, I am the audio recordist, and do both audio and video post-production, and I am also the webmaster. Singerbabe often gets us free drinks, on sheer force of her personality, and the fact that she does promo work for the booze makers. We split equally, and agree to the occasional requests from the BL to pay for biz cards, or equipment repair. Emphasis is on "occasional." Nobody gripes.
We do have plans to move up, in terms of profile, and compensation, but, it would be so hard to determine who deserves what, since everyone does something extra. The prior singerbabe (the notorious violinist, and a superior talent) would not help with load-in, or load-out, and was not a crowd-schmoozer, like the new gal, and was sometimes docked pay, as a result. It's about being a good teammate. All 5 of us sing lead vox, in a 4-hour gig, so it is not about being "the voice" of the band, as the violinist's ego often said. The new gal gets better with every show, and our fans already think that she is awesome (shows you what audiences know; BL and I know that she is maybe 70% of what she could be, in time, which is to say, "dangerous"). She is not afraid of the load-in/out work. We do not ask much, in that area; hold a door for guys moving big, heavy stuff, roll cables, etc. It's all about the attitude and work-ethic, which she has, in spades....and I've known her the longest, amongst the bandmates, and it's less than 2 months, as of this writing.
Sorry to digress, a bit.