Was there news somewhere that the game was going to be released on Steam? I hadn't heard that yet.

Steam has the ability to add non Steam games to your games list but this is for organizational only. They had it on Greenlight but that has since retired.

Per SBS To clarify:

We are using Steam Greenlight as a marketing opportunity.

At a later date we will evaluate whether an eventual release on Steam would be a good idea. One (big) consideration will be the tone of the Steam community. Another (big) downside is the 30% Steam takes from your sales.

We will NOT be releasing to Steam Early Access. Our view is that Alpha & Beta are for testing, not playing. Our Alpha & Beta servers will not be the full game. Features will be added & removed as is needed to test areas of the game. Servers will be wiped a LOT. None of that makes for a great play experience for someone expecting a full game.

Link

The pledge packages available today on the website contain things that will be impossible to get after full launch of the game, whenever that is to happen.

The only way you will be able to get various items will be through gameplay.

If and when the game comes out on Steam, which I'm not sure I have seen anything suggesting it is planned or not, then you will just be paying for the bare minimum to access the game, the packages will not be included.

Source

Get a pledge package now, before prices increase with the release of the game. With your pledge package you get benefits that will not be available to players who join at a later date, plus you get to follow along with development. Soulbound Studios regularly releases updates and receives feedback from the community during development. So choose a package now - you can get access to Alpha and Beta at different pledge levels.

(there are other sources too, but you get the gist)

You will be able to buy Chronicles of Elyria on steam at some point.

Caspian22/04/2018 CoE will be available for purchase on Steam at some point.

We will very likely have our own launcher/patching system. Our choice to go on Steam is solely about making the game more accessible to others. But many games/MMOs such as Path of Exile, Neverwinter, etc. have both their own launcher and Steam store sales. Steam is a great platform for getting your game into the hands of as many players as possible. That doesn't even require integrating the Steam SDK if you don't want to.

Elyria is so large, we have to stream our data either way. So more than likely the Steam experience will be to download the base install, and then launch from Steam or your desktop which will launch the game and begin streaming in the background.

The experience is important to us, so we'll make sure it's smooth as butter. But a PC title - especially for an indie studio - that doesn't go on Steam is asking to be ignored.

That is a quote from Caspian from Discord.

Labbe brings up a valid point, right now the prices of the packages are cheaper as a reward to early backers, but as time progresses they will raise in price, they have rose in price before as well.