Ex Eldar player here. Tempted to sell all my stuff (and i'd say i have nearly every codex unit)
I've found the time investment in a game is too large (a downside of several games, including Risk, Diplomacy, and Twilight Imperium) If you want a good short wargame try Memoir '44. You'll learn it in minutes and enjoy it right away.
Warhammer has many advantages, you learn fine motor skills and creativity from assembling and painting the models, you test memory skill with tonnes of rules and fluff, you apply mathematical skills in when working out what to do in a game, you learn tactics and stratrgey, potentially psychological warfare to psych/distract out your opponent... A huge range of educational benefits.
Thay said fun vs cost? Depends on who you are playing against, i find beardy players to ruin the fun. And getting into a mindset where winning is all that matters ruins it even more (but you've got to beat those beards...) Unfortunately the rules are difficult to interpret at times; with line of sight and cover being contested, distances difficult to judge, and abuse of certain rules just basically unfun. This leads to a lot of potential abuse. Still with the right people you don't have to worry about that abuse.
There are certainly places you could download 3

models of 40k stuff, if you have a 3

printer; i'm not sure if they are still available if thepiratebay is still down - but they may be elsewhere; that might offset the cost (otherwise going with the above suggestions would work well)