How are transaction fees computed For example, how much would the fee be to send $350 to someone? The person is trying to tell me it would cost $270 for 225 bytes
The Bitcoin transaction fee depends on :

The size of the transaction
The current feerate

The transaction fee in $ depends in addition on the price of a bitcoin in dollar.
Simply put, the size of the transaction basically depends on the number of time you received bitcoins in the past (if you want to send 350$ the transaction size will be higher if you received a hundred times 3.5$ than if you received ten times 35$). This is the number of inputs of the transaction.
The feerate depends on the current demand for block space.

The bytes were 225

The estimated fee rate for your transaction to be included in one of the next ten blocks (1h40) is currently of 0.00002121btc / kilovbyte.
The current price of a bitcoin in dollars is about 8800$ / btc.
This transaction would cost you about 0.042$ (to be confirmed in the next ten blocks).
&gt;&gt;&gt; 0.00002121 * 225 * 8800 / 1000
0.04199579999999999