Everyone knows that Steam is the place to go, but numbers!
Weather Factory, the devs behind Cultist Simulator made an awesome blogpost about their situation, including numbers:
itch: 170 units; 3.5k USD gross (but see note 2 below)
GOG: 3100 units; 11 units refunded; 58,300 USD gross
Humble : 7400 units; 135,000 USD gross
Steam : 93,000 units; 7800 units refunded; 1.46m USD gross
total: c.105,000 units, 1.76m USD gross
And it’s a game which had Humble as their publisher (responsible for marketing too), that should boost Humble’s numbers somewhat.
WF themselves write that Steam is the platform you need,
if you’re an indie dev making games for the PC in 2019… you are dependent on Steam for your income.
Can we really say that smaller studios have the choice of not releasing their game on Steam?
WF says yes, it might be viable to use your preferred non-Steam platform, reasoning with the pre-launch preorders exclusive to itch (reduced price, comes with Steam key on launch),
in those three months, we sold 1,070 units on itch, and after launch, when the game was available on Steam, in seven months we sold 178 units
showing that players are not “locked in”, are willing to use different platforms if Steam is not available… but that pre-order came with a Steam key.
I have my doubts.