You really think you can independently afford high speed localized 24/7 file hosting all over the world for potentially millions of downloads for less than 30% of your sell price?
Steam games can be cheap because steam offers all the expensive things cheaply. No one is going to download your game off of a shady MEGA link. No one is going to go to fucknuts.biz.co.uk.nz to your shady site straight from squarespace templates to then crash your filehost by trying to download your game at the same time as 500 other people. No one is going to trust you with their bank details and crypto is a scam and paypal also takes a high cut.
If your goal is to do gaming more than a thankless, pay free hobby you need:
Marketing
Trust
Payment Provider
Accounting (tax is different in every country, and you have to account for that in every country you sell your game to)
Global CDN
And ease of use.
Unless your game is so incredibly niche AND so incredibly good that you can get away with shunning all of those things, you will need those to make enough money to even make a minimum wage salary after a year. Starsector and dwarf fortress are the only ones that come to mind, and the latter went to steam after Tarn decided to actually go full time and needed a real income to cover hosting and salary that couldn't be found in donations.
Data centers are expensive. And yes profit is built in to steam's cut because they know most players aren't going to repeatedly download any given game over the lifetime of their steam account. But doing it yourself means either you do not offer repeat download to players, or you run out of money in two years because people stop buying the game but people will still download it again and again.