What will be the fee in $ for a 500$ transaction ?
Fees are not based on the amount being transferred, but instead on the amount of space the transaction occupies.
For a very simple transaction with one input and two outputs, you would occupy a few hundred bytes of space.
Moreover, fees are decided by you (or the exchange/hosted wallet service you make a withdrawal from). The fee paid is simply the difference between the total input, and the total output.
For example, if you have an input of 1 BTC, and an output of 0.99 BTC for a transaction that occupies 100 bytes, the fee is 0.01 BTC, or 0.00001 BTC per byte, which is known as the fee rate.
The fee rate is continuously calculated by most wallets as network conditions change, and can be as little as 0.00000001 BTC per byte during times of low network congestion.