Valve is worth maybe 0.1% (single digit billions is what I’d guess) of Apple, which made $112B in net income in 2025. That’s profit, not revenue.
Apple could probably buy Valve for 30 days of its net income, which is around $9.3B ($306M per day in profit, including weekends)
There’s zero chance that Gaben has squirreled away Four Trillion Dollars in cash.