What's the explanation for certain high fee transactions/blocks?

Question

From my understanding transaction fees are calculated automatically based on the transaction size in bytes, the current average block size, etc. I've noticed recently that transactions have been appearing with 0.2 monero transaction fees despite being nominally the same size as other transactions using 1/10th the fee. For example: https://monerohash.com/explorer/block/1283872

Obviously any miner will gobble up these high fee transactions and prioritize them in any block they are constructing -- the miner that found the above block got nearly 1 extra monero vs. the average block reward.

Any idea what's going on here? Does the monero wallet have an option to specify transaction fees I'm not aware of? Why would someone (purposefully or otherwise) pay so much (nearly $4 in USD) in fees for a transaction when at a time the mempool was nearly empty and their transaction would appear in a new block shortly regardless?

Answer 1

From my understanding transaction fees are calculated automatically based on the transaction size in bytes, the current average block size, etc.

That's right. It's the minimum fee, and the fee (per kB) is actually calculated based on only the current block reward, and last 100 blocks median block size. The constant parameter chosen means that the minimum fee is enough to make it economic for the miner to expand the block size for exactly 0.6% as it wold result in the biggest earnings per block.

Does the monero wallet have an option to specify transaction fees I'm not aware of?

There is a setting in the wallet offering 3 priority levels: 1, 2, and 3. The first level is your minimum fee, 2nd level is 20x that, and the 3rd level is 166x the min. fee. After the HF, there will be 4 levels with x1 x4 x20 and x166 multipliers, where x4 will be made the default. Note that due to HF changing the min. block size, the x4 will cost/kB the same as x1 does right now. This will make x1 a kind of "low priority".

Anyway, monero CLI wallet allows you to set the level to use with set priority <level> command. Thing is, it remembers the setting for all following transactions.

Any idea what's going on here?

We can only speculate. Maybe someone needed to move a big amount urgently for catching some trading wave so the high fee would not really be an issue considering the value of a transaction. If he forgot to set the fee back to low, he'd be accidentally making high-fee TX-es even after the rush-hour.