I’m not sure: is the Gallium a catalyst?
The advantage of using gallium is that it is in liquid form. When the gallium is regenerated after catalyzing one cycle of the reaction, it mixes again with the liquid gallium.
Being liquid ensures a long life for the catalyst. Solid catalysts are never recovered perfectly after taking part in the reaction and then being again deposited on their support, so they degrade much faster.
The mechanism of solid catalyst degradation is similar to that which limits the life of a rechargeable battery with solid electrodes.
Gallium is one of the most expensive metals, not because it is very rare, but because it is very diluted. There are no minerals with a high concentration of gallium, enough to make their commercial exploitation worthwhile.
There are no mines of gallium. Gallium is always extracted as a secondary product in mining operations where either aluminum or zinc is the main product.
Because of that, the available quantity of gallium depends on the volume of the productions of aluminum and of zinc, and it follows their yearly oscillations.