I started reloading when I got a Swede and nearly had a coronary at the price of ammo, then available only from Norma.
Reloading is an end in itself - you can't justify it from a cost basis, but it's fun, you can re-create expensive and hard-to-find ammo, and you can lie to yourself that you're only paying 25 cents a round for those .222 mags. When you're done reloading, if ever, you can sell the equipment and recoup most of your cost. It's a trivial investment when you consider that you'll be using the equipment for decades. i bought my Rockchucker press in 1982 and I'm still using it.
If your cousin wants his son to shoot deer with that rifle, he should put the money into reloading equipment instead of into a couple of boxes of ammo. Just my humble opinion.
ps - I wouldn't shoot someone else's reloads in a borrowed rifle, let alone my rifle.