The cost of minting an NFT is based on a number of factors, including the gas fees that miners pay to validate transactions. These fees are a small fraction of Ether and will fluctuate with the price of Ether. Other costs include account fees, which vary by marketplace. They can include fees for boosting accounts and other transactions.
There are a number of ways to reduce your costs. The easiest way to do this is to make use of a service that charges a lower gas fee. Many minting services are free, but some platforms will charge a fee. The best option is to choose a platform that charges less gas, which will allow you to mint thousands of NFTs without incurring additional fees.