This $1.2b in Steam sales is cumulative since around August 2020, so a period of just over 5 years. We can say $240m per year on average.
Their last annual financial statement said that they made $2.8b profit for the year ending March 2025 from their "Games and Network Services" division, so subtracting the ~$240m of Steam sales would leave about $2.56b from PS5 and PSN sales.
That's about 90% PS to 10% Steam. It's a nice extra market for them, but it's not make or break.