They cost as much as a gas set up and then the blocks are much more
expensive.
You can also add as many needle valves to a regulator as you have tanks
you want to add CO2 to.

Over time, the gas tanks are a better deal.
If it's a smaller tank, 55 gal or less and you need space, this might
be useful, but they do break and wear out. I've had the same gas tank
set up for 15 years.

You can get a reg for 69$ with solenoid, needle valve, I bought a CO2
20lb tank at the fire extingusher place for 50$ filled. Cost 12$ to
refill which will last 3-4 years on a 160 gal worth of tanks.
You can do the the rest of the math.

Regards,
Tom Barr