I caddied at an upscale club 15 years ago, $20 was the cost for a high tier caddy who could actually offer advice and knew all the etiquette and knew the course well. $5 was the cost for someone to carry your bag for you, IIRC you got a set amount from the club depending on rank (there were 3 or 4) just for walking the course so you'd at least get something.

Tips were largely subjective, but the norm was to get a tip equal to your cost, but for large events like cups or competitions or charity events, you got a higher wage from the club and it was all hands on deck, everyone was going out. Depending on circumstances, the club may provide the caddy at no cost to the golfer as well. On those, the expected tips were around $20 regardless, but again this was largely by tradition of established club members so visitors or newcomers were usually widely over or under tipping, in the range of a couple of dollars and a stick of gum to several hundred dollars.

It's possible he was art a new course or never before had a caddy and tipped ignorantly, or that he's a stingy bastard. Hard to say without more details.