Jerky. If you're fishing for the day, you need to bring enough Jerky for everyone, preferably cured at home and from an animal that you killed yourself. This is a kind gesture that will start a conversation and a friendship, while stimulating the taste buds. It's 1000 times better when 2 people who meet for the first time start by exchanging pieces of jerky.
Going back to the O.P., I believe the clear definition of a co angler giving an angler money at the end of the tournament that non boaters are eligible to compete in is called a tip. Calling it exactly what it is, a tip, should clarify a lot of thinking here. If tournament rules say co anglers kick an extra $50 for gas and the co angler doesn't pay, then there's a complaint. If the rules don't, then sorry, that's the rules of the tournament that the boater chose to fish in, perhaps they should choose to sit that one out next year.
Now that we're on the subject of tips, let's talk common courtesy. C'mon, man, if you just kicked up $500 in tournament fees, you're carrying 5 top of the line (or even middle of the road) rod/reel combos at $750 a piece, your tackle bag looks like Bass Pro Shops should be buying gear from you to stock their shelves, and you can't kick in a few bucks for gas and an extra sandwich, you're probably best described by words that mods will yell at me for saying. If this sounds familiar, I hate to break it to you, but you're "that guy." Don't be "that guy" and you'll find that your life can be so much better when you're not finding subtle ways to push people's buttons. The same applies if you're the boater, your angler has a couple of hand-me-down rods, old lures, and he had to stash a little cash in his tool box for the last 15 paychecks just for the opportunity to get out and fish one tournament that year (even though he might be the one most likely to feed and tip you, and he's not likely to be anywhere with a $500 entry fee). You are, however, in a tournament. This tournament is a competition with rules, and like any other competition, competitors are free to utilize every advantage and disadvantage in the rule book. Don't like the rules? Don't fish the tournament, don't join the club, whatever it is that you're prepared to spend the next 3 months whining about, just don't.
If there's no tournament and you're just out fishing, if you planned to fish the tournament together and there's no random drawing, if you're angler and co angler are in a team tournament, if the boat's a cabin cruiser and there aren't any fishing poles, or quite the number of similar situations, then we're on the subject of a conversation that should have been had before you were anywhere near the water.