> How can that possibly make sense?
Well, here is the operating profit for the US tech giants:
Apple $100 billion | Microsoft $70b | Google $62.6b | Facebook $44.5b | Amazon $29.6b | Intel $22.7b | Oracle $15.7b | Cisco $13.7b | Qualcomm $10.3b | IBM $8b | Texas Instruments $7.7b | Broadcom $7.6b | Nvidia $7.3b | Micron $6.7b | Applied Materials $6.4b | Netflix $6b | Dell $6b | Adobe $5.5b
SAP is one of the primary tech giants in Europe. Their operating profit is $6.2b by comparison (they fit in Microsoft's pocket these days).
Now on top of that, throw in the US banks which are generating enormous profit compared to their European peers, and they also hire tech talent. Throw in Visa, Mastercard, American Express, Square, PayPal, Stripe, etc. Then throw in the US defense contractors. The large pharma & biotech companies. Insurance companies. Huge retailers like Walmart, Costco, Home Depot, Target, Lowes, Walgreens, CVS, etc. Big real-estate companies. Various large conglomerates and manufacturing firms. All of these companies - which generate outsized profits as well - have to compete for tech talent too. The point being, all that demand drains availability and pushes up the salaries that tech talent can command (including outside the bay area).