Ammunition is much less expensive, so you feel like you can shoot more. If the ammunition is less expensive you feel like you can buy another handgun or two. Add the price of reloading equipment and reloading has cost me ~$1000 more than if I weren't reloading. I suppose I can make it up in volume.
Additional exercise. Lots of quality time policing brass with bending and stretching exercises.
Ability to nod sagely when discussing the advantage of 4.2306785 grains of Bullseye is better than 4.0033578 grains of W231 for bullet weights of 200.003 grains to 200.005 grains.
The fact that non-reloaders think you've really gone to the next level and really know stuff. Scary when they start asking me for advice and I'm hoping (a) the bullet comes out of the barrel and (b) if it does, pieces of barrel don't hit anyone.

New, strange compulsions to look at lead melters and .45 SA revolvers. Think how much you can save by casting your own bullets, why it would pay for the Blackhawk in no time at all.
The strange notion that to get my workbench back, I have to build a reloading bench.
If TV is dull, just go out and knock out a 100 rounds.
Did I mention the treatments for tendonitis from pulling press levers?
Obviously, the benefits of reloading outweigh the costs. Besides, the last time I calculated the cost/pound of my other hobby, fishing, delivered gourmet fish were less expensive.
Second childhoods are great. You can have so much fun.