Lets put it this way:
Unless you are trying to cool a whole 250kw Tank with Novec and 2-phase immersion cooling, it doesn´t make any financial sense.
The only reason why immersion cooling is cheaper than air cooling ist because of scale. When you put many units into these tanks, less liquid is needed and at some point the liquid becomes cheaper than buying heatsinks and fans for your units.
Why would the cost not scale down? Whats preventing you from having the same gallon/kw ratio with a 10kw tub vs a 250kw tub?
-Bulk quantities of liquid are way cheaper.
-A small tank is more expensive per volume created than a bigger one
-You need to build a custome lid with air pressure control and access for the water cooled condensers
-You need to build a water cooled chiller and install it in a safe and secure way in your tank.
-The radiator for the chiller needs to be built into an existing structure, i.e. your building in a safe and secure manner and some kind of fan mechanism might be needed
One time costs of this are far higher per W when only a small radiator is installed.
-A water pump for pumping your water to the outside will need to be installed. Big pumps are way less expensive / waterflow than small ones
-Labor on a small project is far more expensive per kw than on a bigger build.
-Bulk materials purchase is far cheaper per kw cooling in a big build
I could go on. Please admit that building a small immersion cooling rig is far more expensive per kw than a big one.
The whole point behind cheap immersion cooling is to from the start design boards for immersion cooling, which will be cheaper than regular units as you dont need to buy and install heatsinks and fans.
Additionally you can put a higher amount of chips on the boards, as you dont have to think about cooling layout etc.
The savings from board / heatsink / fan costs and the labour installing those is then put into ~200cc fluids per kW, this apparently costs around the same.
Further savings are then achieved by lower maintenance costs, as you can "build" your own custom datacenter by just buying a shipping container for around 700K from Allied Control.
All you then need to do is hook up around 1,4MW of power and you are ready to go. No costs wasted on racks in datacenters etc, only electricity costs and small internet fees.
When it is time to upgrade your gear, the real cost savings come through as liquid and tanks etc. are already installed and you can just switch out the boards.