There seem to be some unpleasant intellectual property issues with vanadium, else surely more than a handful of companies directly tied to the original invention would be producing units?

On the one hand, I've seen low vanadium electrolyte costs estimated for large volumes, like $50 to $150 per kwh of capacity. On the other hand, I hear of very high system costs, and limited storage. For the example you state, it would seem to be a simple and cost-effective matter to just add a lot more vanadium flow storage, yet that seems not to be considered.

Volumes of scale and process refinement could likely help, but that requires some outside money and intellectual property access.

Here are vendor-stated costs for the vanadium battery:

The assumptions used for the cost of the 5 kW stack and the electrolyte system respectively
were:
Stack cost $5,410
Electrolyte cost $118 / KWh of storage
For example, for 8 hours or 40kWhs of energy storage, the electrolyte cost is $4,470 giving a total
capital cost of $10,150.

Unfortunately, they say this is a "target" based on volume manufacturing and a 2x sale-price mark-up. I don't know of many companies that survive on 2x for relatively high-tech products while supporting an engineering wing, so those numbers are probably a long time coming.