I own around 200 skins on my LoL account.
Riot's site says I spent $1310 on it.
i bought 3 skins in 2018,
4 in 2017,
6 in 2016,
20 in 2015,
40 in 2014,
73 in 2013,
33 in 2012,
6 in 2011,
9 in 2010.
During 2012-2014 I didn't buy many other video games (maybe 2-3 a year). I haven't put any more money into it since seeing how much I spent, lol. I don't really play LoL anymore outside of occasional casual sessions with friends.
Probably 100-200 was spent on gifting to friends.
I think ME3 Multiplayer and Halo 5 are the only other games I've spent big money on, but not nearly this much. Maybe like $100 a piece.