There's a helium shortage on and though it might get better in the distant future, I'm not holding my breath. Places like Harris Teeter no longer give kids helium filled balloons because it's too expensive, and a generation of nerds risks growing up without witnessing firsthand the enhanced humor value of dirty jokes told with a squeaky voice.
Today I swapped out an "owner tank" (small compressed gas bottle where you own it, as opposed to paying demurrage to rent a tank from the compressed gas company). These are the same size as the 20-pound CO2 tanks that one sees connected to soda fountains, not the big cylinders that one typically sees in welding shops or at fairs for filling balloons.
Four years ago, a full owner tank was a shade under $70. Last year it was $78. Today it was $87 and change plus tax.