According to https://coinmarketcap.com/nft/collections/, BAYC average price is currently at 75.54 ETH, which is mean that is the average of the prices of all BAYC NFTs. You can take a look over https://opensea.io/collection/boredapeyachtclub, to see all of the listed prices.
The CMC methodology to calculate market capitalization as follows.
Let (S) be the current circulating supply of Bitcoin.
Let (D) be the derived market capitalization for Bitcoin.
For this example, let (C) = 10,000 USD / 1 BTC and let (S) = 17,000,000 BTC.
D = C * S
D = 10,000 USD / 1 BTC * 17,000,000 BTC = 170,000,000,000 USD
Although it doesn't clearly tell it applies to NFT and estimated data, we might assume it also can be used for NFT data.
So the formula can be calculated as 75.54 (avg price) * 9998 (total assets/NFTs) = 775.244,92 ETH