inelastic

Lacking elasticity; inflexible, unyielding.

He spoke languidly, and only those few words, like a watch with an inelastic spring, that just ticks a moment or two and stops again.

I cannot believe that Christ himself intended that his religion should be so inelastic, so hard and fast, so cruel as you imply.

Insensitive to changes in price.

perfectly inelastic supply

A different approach is needed now, as there is more discretionary travel which, unlike the use of season tickets, does not have inelastic demand characteristics.

Resistant to swings during elections; predictable.