A Noble Gas
As the price of Helium increases the cost of things like MRI Machines, even running them because there is always some leakage, goes way up. It is equally true that we throw most of it away, it’s literally as cheap as dirt so at the moment there’s no incentive to price frivolous uses like Party Balloons out of the Market although there are restrictions in supply due to bottlenecks in transportation infrastructure.
And like it’s every place there is Natural Gas (though some are denser than others) which is everywhere so anyone willing to invest money in the capture is almost sure to find all they can sell. Clearly there is a natural cap on demand which means the Market is saturated in the stuff.
Will we ever run out? Well, we never thought we’d run out of Passenger Pigeons and Buffalo until we did.