Yes, every payment merchant applies transaction fees - the fee you pay will vary based on whether a sale is made on the Marketplace or in your personal store.
Each personal store sale will be subject to either:
PayPal fees - detailed here
Or Stripe fees - detailed here
Marketplace sales won't be subject to individual fees, as you'll be receiving one payout for all your sales, meaning you only pay a transaction fee on that one payout. The amount will depend on your chosen payout method, with Wire Transfer fees being exceptionally higher than other methods. For the lowest fees, we recommend choosing Check, Bank Transfer/ACH or PayPal.