I had a couple hundred on E:WOM, then a few more hundred on FE - quite a bit of betas, now 170 on LH including betas. So, probably 600-800 hrs so far on this franchise - for a pre-release purchase of ~$60 of E:WOM. Holy crap.
For me I really think its the moddability. I can use someone elses mod, tweak the game files myself, cheat, anti-cheat, do stormworld/affliction type changes. Crazy.
Plus while my wife isn't terribly thrilled with how much I play - she acknowledges that it is a) cheap and keeps me home.