Rather, the only thing that will truly motivate TSMC to take on more risk is competition. 

I see it another way for more chip manufacturing capacity.

If big tech wants TSMC to increase capacity drastically without TSMC having to take all the risk of CapEx, then they can pre-pay for wafers from TSMC.

They can each give TSMC $10b now in cash and guarantee themselves wafers in 2-3 years that it takes to bring a new fab online.

TSMC is rightfully conservative. If they commit to spending an extra $30b on a fab now that won't make a single wafer until 2029, without any guarantees from big tech, they're stupid. Who knows if the demand will still be there (my guess is yes, but who knows?).

In my opinion, I think it's getting close to this. Nvidia will surpass Apple as TSMC's biggest customer this year. This will start a war for TSMC wafers in 2026 in my opinion. When you have that much demand, customers will be forced to pay well in advance.

There is already a war for memory, silver, copper, energy. No reason why chip production won't be next.