Avowed will be available on Battle.net, which means you can buy it for about 1.4M gold in WoW if you want to

pcgamer.com:

It's time to start gold farming in World of Warcraft because Avowed is coming to the Battle.net launcher when it releases next year. You can pre-order Obsidian's big fantasy RPG on Blizzard's store right now, including the premium edition that includes five days of early access to the game.

That means that, with some effort, you could acquire Avowed by farming gold in WoW. According to this site that tracks the price of WoW Tokens, a game time voucher WoW players can buy for in-game gold and convert to $15 of Blizzard bucks, they're selling for about 273,000 gold. You need five of them to buy the standard $69.99 version of Avowed, which means it costs a total of around 1.4 million gold.

Most people don't have that much gold lying around unless they're the kind of WoW player who spends their time running old dungeons for rare items or plays the auction house. You really have to commit to filling your bags with that much virtual cash, but Avowed won't be out until February 18, so you have some time.

This whole thing was a surprise. So far, the only non-Blizzard games to appear on Battle.net have been Activision games, and Blizzard recently started releasing games on Steam for the first time in its history. But in hindsight, we might've seen it coming: Microsoft didn't pay $68.7 billion (roughly 4.6 billion WoW Tokens) to buy Activision Blizzard for nothing, and has also added «included with Game Pass» text to Battle.net pages. It may as well release games from its other developers there, although it seems like it's being selective about it. As a fantasy RPG, Avowed fits in easily with Diablo 4 and WoW, but will we see Microsoft Flight Simulator there, too?

You can, of course, still buy Avowed on Steam or subscribe to Game Pass Ultimate for boring human money and play it on release. It's surely the smarter way to get the game, but it's also the less adventurous way. You never know, the next Halo could show up on Battle.net and you might be kicking yourself for not