Perhaps the helium price is right, but argon is certainly much cheaper.

That price of argon might be per cubic meter, not per liter.

The price of argon is essentially zero for the argon itself, which forms one percent of the air. What you pay is only the energy required to separate it from dioxygen and dinitrogen, e.g. by liquefaction and distillation.

EDIT: Googling now, I see prices for argon around half of dollar per kilogram.

A cubic meter of argon has slightly less than 1.8 kg, so the price of argon is at most 1 $ per cubic meter.

A liter is one thousand times less than a cubic meter, so the price per liter is one tenth of a cent.

You likely meant to write 'xenon' there, not 'helium'. FWIW, https://en.wikipedia.org/wiki/Xenon has

> Because of its scarcity, xenon is much more expensive than the lighter noble gases—approximate prices for the purchase of small quantities in Europe in 1999 were 10 €/L (=~€1.7/g) for xenon, 1 €/L (=~€0.27/g) for krypton, and 0.20 €/L (=~€0.22/g) for neon,

I buy a big tank of argon periodically for TIG welding. I don't remember what I last paid but it was cheap. Decades ago I used helium but it's much too expensive for hobby welding now.