Golf Balls
Bingo!
You just discovered Law #1 of Capitalism: Let'm buy.
If you look further into the Pro Shop, you may be the first to discover that these ball have durability dots, individually for each type. That means they wear in different intervals.
Other dangers for the custom balls include weed, water, gorse and OOB. Don't go looking for them, you will never find one there, and there are no "experienced balls" available at the counter.
Which brings me to RL: A caddy taking us on tour of the Old Course of STA on free-of-play Sunday found a ball under a gorse bush. Picking it up he told us that he had never payed a penny for balls - a lucky man!