To support a QRSS Beacon Balloon effort (see previous post), I checked with the local Welding Gas Supplier, a large standing tank of Helium is about $110 plus tank rental. The tank can be rented for about a week (used at parties) for a few dollars, or by the month for commercial accounts at $20 / month. To purchase a tank it is about $450 with refills at the same $110 rate.
I think the rental rates includes a regulator. But, to buy a tank would require an additional $45 for a regulator.
I need to do some more Beacon Balloon planning before investing in Helium.