What do you think about this?

Hi, I'm developing a one-vs-one videogame with multiplayer and local option. My idea for launch would be a version for Steam and another for web. The game has unlockable contents, in the web version the unlockable contents would cost 3 times more than the Steam version.

Also the Steam version includes the soundtrack produced by me.

An example?

This is a track for my game published on android

https://soundcloud.com/shaoo/non-stop-robot-android-ost?in=shaoo/sets/non-stop-robot-android-game-soundtrack

The contents are unlocked by winning rounds, this will allow me to keep active users in the game because, as I said before, on the web they cost 3 times more effort but you will play for free. In the version of Steam the unlockable contents do not require so much effort. For example, to unlock a new level or character in the web version you will need to win 40 rounds, in the Steam version you only need to win 20.

At first I think it's a good idea.

Any suggestions? Has anyone done this before?

I don't profess to know if it's a good idea or not, but here are some considerations, assuming you mean for the Steam version to be a paid game...

Steam's advantage as a platform is that it has huge reach. Steam's disadvantage is that they take a large cut of your revenue. It would make more sense to me to have the free version on Steam to leverage the reach and the paid version outside to collect the cash.

Developing two versions of a game is additional work and possible bugs/maintenance. Especially when it might not be necessary to have two different versions at all. Why not use the same business model for both?

People can react extremely negatively to pay up front games that act like freemium games in disguise (SW: Battlefront 2). They can also react badly to freemium games that hit users with a huge wall to progress locked behind IAP, essentially becoming pay to win. It sounds to me like your approach is to do both. There can be a good balance in the middle somewhere, but then you would only need that one balanced system and not two separate versions.

All my personal opinion - I have no experience publishing games.

Thanks for the opinion.

It makes sense what you say, I should think about it.

The game does not require additional purchases, the contents are unlocked simply by playing and winning games.

Selling the paid version outside of Steam, how would I sell the paid version if I do not put it on Steam? I have no idea about that.