I've a small SPEHSS MARHEEN force, about 35-40 models and one METAL BAWKES, and a teeny, tiny Eldar force consisting of a Farseer, 10 Dire Avengers, and a Waveserpent. One day I'd like to acquire some more Eldar, but I have a feeling that will probably never happen, given GW's penchant for price hikes.
Opinion alert!
All in all, I'd say 40k is the worst tabletop game for your wallet possible. Which is a shame because of the four I've played and watched, 40k is, by a large margin, the best. And that is despite the idiotic was GW does Codecies, the game's current anti-close combat rules, and the general Tau worship that the QA testers seemed to have overlooked.
Warhammer Fantasy is just so slow and I hate stupid rules like charge blocking. Sure, it makes sense if there is a large block of spearmen or something in your way, but it works with literally any unit in the game. "Oh, I have a lone, wounded dog between you and my ballistae. Guess what you can't charge? Hint: The ballistae."
Warmachine/Hordes is too tedious, with all the micromanaging of single models and the anal retentive fixation on precise distances. If I wanted to micro a bunch of lame looking models, I'd just play Starcraft.
And then there's Infinity. I like Infinity. It's just not as fun as 40k. That said, Infinity is cheap and the models usually look awesome. And the ARO and stealth mechanics are really fun. But there's something about 40k that just wins out in my book.