I believe the Manhattan project (where we basically built an entire new city, and entire new manufacturing process from scratch: mining operations, refineries, enrichment, milling, etc.) cost less in constant dollars than the stealth fighter.

They also had a strong ideological element too.

The talent + purpose (which drew the talent) was what defined Manhattan. The money came easy when all of the greatest minds in the country were pointing a giant flashing light in one obvious direction.

This is big news but fusion will largely be a product of the people it attracts. The people can do the job attracting money and other talent if it's justified.

I've seen the Canadian gov try to throw money at trying to build a local tech scene and it all went to hucksters, old school finance suits with megacorp resumes, and administrators. While all the tech talent just kept going to SF where the capital was going into high risk ventures... not expensive buildings, events, 'entrepreneur/small business programs', and propping up old school D-round investors. Money is easily wasted even when the pursuit sounds noble and valuable on the surface.