And if the Big Tech companies think it is so important to get all those compute and/or memory chips sooner and in larger supply, it should be no problem at all for those Big Tech companies to pay for the costs and then have priority access to all (or their portion of) the output for the future years.

OTOH, if they are insisting on not investing their funds or stock, and it is simply pressure on TSMC to take on the risk, TSMC should be very wary of taking on risk for those players (unless TSMC sees another advantage of producing into a likely glut or supply canyon shortly after the new fabs come online).