That's what I do
I'm not sure there's any TRUE justification for buying that many games, but once games truly become your hobby, even spending that amount of money on it is not really that bizarre compared to other hobbies.
It also helps that it's diffused over such long periods of time. It's not like I walk into a store and shout "Give me 100 ds games! here is my roll of bills", it slowly adds up over years and years.