I suppose if you are buying it all new, the cost comes out the same. Certainly, $50 for convenience is not out of hand. FWIW, however, you can usually find a deal on a mini-fridge on Craigslist and that would save potentially $150 off your cost. Craigslist can be incredibly inconvenient, however, so I totally understand if you don't go that route.
For me, multiple kegs is less about the quantity you drink than having variety. For example, I don't necessarily want to drink 5 gallons of wheat beer although I have a keg of wheat on tap. It's nice to open the fridge and have that second keg as an option. I will also swap kegs out before they are empty if I get tired of them or just want something else. But it's a PITA to want variety and then to have to wait 24 hours or so for the new keg to settle and cool to serving temp.
Finally, the keg shouldn't spoil unless you have an infection. I've got some beers that have been kegged for over a year with no problems.