From the NEO Whitepaper:
"GAS is the fuel token for the realization of NEO network resource control, with a maximum total limit of 100 million. "
It isn't any more rare than NEO even though it is displayed as 9 million on CoinMarketCap. This is a common misconception being spread on social media etc.
RE: NEO GAS is the equivalent of ETHER and it's a hidden gem