I have no deep understanding of NFT's but I want to share my guesses.
They are probably using classical off-chain methods (using a database) to hold your created NFT until someone pays for transferring it. I think there's no meaning in paying entrance price. They also take commissions for every transfer that is around %2.5
Ethereum network is super ...
Binance Smart Chain is cheaper and faster today, but I am not sure why because if you see the gas averages charts in the official scans sites you can see that the BSC costs are so much highers than Ethereum.
I think is because the BNB value is lower than ETH value.
Each block has a gasLimit field. A miner can increase or decrease it. This change is small, less than 0.05 % of the parent's value. So it cannot be changed immediately to an arbitrary value, usually changes have to be applied for several hundred of blocks before it reaches a particular value.
Now there are three situations with respect to miner gasTarget and ...
Deploying my contract on rinkeby cost ~12 USD in gas fees
Your gas fees are a function of
a) the gas required for deploying the contract, and
b) the gas price you've chosen.
b) can be altered, but with a lower price usually equating to a slower transaction. If it's much lower than the rest of the current market, then it's unlikely the transaction would be ...
Usually it is safe to leave the gas estimation for the wallet itself and not to try to do it yourself.
In the case wallets cannot estimate the gas, which sometimes happens for complex transactions, you can do test transactions on testnet and figure out how many gas units the transactions spend and then use that as a hardcoded limit.