Would it have been possible to change to a cheaper menu while still keeping the Michelin star? There's plenty of affordable — and even cheap — Michelin starred restaurants.
Also, I could be wrong but I thing the "Michelin starred food truck" and other cheaper starred restaurants are all outside France, in France there's still much more of a common standard that Michelin starred restaurants feel they need to live up to including experience and price.
And of course, it's much better to renounce the star than to lose it.