You can follow this guide in order to fetch the stripe fees per transaction:

// Set your secret key. Remember to switch to your live secret key in production.
// See your keys here: https://dashboard.stripe.com/apikeys
const stripe = require('stripe')('sk_test_....');

const paymentIntent = await stripe.paymentIntents.retrieve(
  'pi_...',
  {
    expand: ['latest_charge.balance_transaction'],
  }
);

const feeDetails = paymentIntent.latest_charge.balance_transaction.fee_details;