How much does it cost to go through a travel agent?

Excuse me, I was wondering if you could clarify something for me. I'm considering booking a trip through a travel agent, but I'm not entirely sure how much it would cost. Could you provide me with some insight into the typical expenses associated with using a travel agent's services? Are there any hidden fees or additional costs that I should be aware of? I'd really appreciate any information you can offer on this matter.