You can see the changes in gas ratios in Etherscan in real time.
Gas costs fluctuate depending on the congestion of the blockchain, and especially when NFT's public sale proceeds, transactions flock, resulting in a momentary five to ten times higher gas costs.
Please note that the gas cost of one recent NFT has been consumed by about 0.03-0.04ETH.
When purchasing NFT, purchasing multiple simultaneously saves gas costs.
2 purchases (approximately 20% savings), 5 purchases (approximately 50% savings), 10 or more purchases (approximately 55% to 60% savings).
In the case of public sales (public sales), transactions are concentrated and the gas cost increases instantaneously. Since then, the gas cost will fall to an average value only when NFT sales are completed, so if you try to purchase NFT when the gas cost is low, it is likely that NFT sales have already ended.