Out of all the MOBA's, this one requires the most time and money investment.
I played LoL for about 3 years and even till now after spending a good $150 from all discounted champions I still don't have all the champions nor runes. Aside from the fact that levelling up to 30 takes AGES, if you're not at level 30 you will not win games because of the lack of access to greater runes and masteries - and because LoL is super snowbally, these things are a MUST to win early game trades. And you have to spend money on runes and rune pages, and on meta champions, to the point where you will be forced to spend up to $30-40 and ~1 month of levelling just to play your first unranked match and feel confident enough to win it. And by that time, your pool of champions and runes are still very limited. You can compile the 6300 needed for new champions or runes, but that can literally take forever to do - if you do only daily wins, that's one champion per MONTH. There are discounted heroes, but only 3 per week and there are 126 in total, and over time the prices really do rack up.
I stopped playing LoL for a few months and moved on to other games, like SMITE and HotS. I only played DotA for one day and decided not to play it anymore because the mechanics are way too unforgiving. However, in the case of DotA, the fact that EVERY hero in the game is free is something that is to be commanded for that game - you can create your profile and play your first ranked game right off the bat.
SMITE is pretty much the same thing - I thought SMITE would in the same boat as LoL, but I was so wrong. All you need to do is to pay $35 on the complete God pack, and you're all set - you don't need to level up or do anything else; you can just go and play your first ranked match comfortably.
HotS is also very pricey, but thankfully you only have to pay for heroes. Resources are also easier to get in HotS, because you can get daily bounties up to 800 gold (one hero costs 10,000), and levelling each up to 5 awards you 500 gold. There are also plenty of hero packs that have price discounts up to 75%. I played HotS for 4 months, paid every discounted heroes and right now I own 90% of all the heroes.
So why? Why is it that Riot makes LoL the MOBA games that requires the most money and time investment?