Steam Greenlight ended in 2017 and was replaced with "Steam Direct", which introduced a 100 USD app fee.
The app fee.
There is now a $100 recoupable app fee for each application to release on Steam. Steamworks developers will pay this fee once as part of the initial paperwork, which will unlock the first appID. Once all the paperwork has been completed, and the developer is set up in Steamworks, additional appIDs may be purchased for $100 each. This fee for each appID is returned in the payment period after that game has at least $1,000 in Steam store or in-app purchases.