As a support agent for a non-custodial wallet company I ran into many a user that had little idea how bitcoin transactions are calculated. Over time I developed an explanation that I believe hits the mark. We will use one of my transaction IDs to discuss the details.
Imagine an empty jar. This jar represents the next block in the blockchain. Since Bitcoin transactions fees are calculated by how many inputs you need to add to the block to create your send think of each one of these transactions as a marble. The more marbles you need to put in the jar, the more space you take up in that jar and thus the more it costs you to send the transaction. Here is my transaction below.
Using this transaction you can see that I needed 2 inputs to create the necessary amount to send the BTC to the other wallet. However, if you receive many little transactions into your wallet like micro payments, faucets or mining payouts you may need more transactions to send your given amount. Since you will be adding more marbles into the jar the transaction will cost you more money because you are taking up more space in the block. So if you run a miner make sure your payout window is rather large as to not cost you a small fortune of your mining profits to send you hard earned Bitcoin.
I hope this explanation was helpful and see you on the blockchain.