Helium is quite expensive, and a limited resource: http://www.popularmechanics.com/science/health/med-tech/why-is-there-a-helium-shortage-10031229 http://www.p

Helium is quite expensive, and a limited resource: http://www.popularmechanics.com/science/health/med-tech/why-is-there-a-helium-shortage-10031229 http://www.popularmechanics.com/science/health/med-tech/why-...