how travel agents make money and what it costs you?

Planning is half the fun, right?  I think so, that's one reason I became a travel agent.  Before I earned my travel consultant wings over a dozen years ago, I planned our family vacations looking at numerous aspects of the trip.  The two MUST HAVES for my family's vacations are EXPERIENCE and VALUE.  Those are two big words serving many wants and needs.  EXPERIENCE changed with every vacation.  What was the mood we were going for -- relaxing at the beach, adventure in the mountains, theme parks and resorts, cabin in the woods, visiting family on a road trip.  Each of these moods had questions to answer -- time of year, budget, length of the vacation.  VALUE had several meanings as well.  Although I am thrifty, I won't book a "bargain" vacation that ignores experience or safety.  Value doesn't mean cheap, it means taking other matters into consideration.  For example, if my family budget for a Disney vacation is $10,000 that might mean staying at Disney's moderate resorts during high season for a week or at a Disney deluxe resort for 10-days during low season.  Experience and value play the most important roles in my vacation planning.  
Then there are the boring but important topics to address.  Is travel insurance the same as medical insurance, is Covid-19 covered, what happens if I have to cancel, do I need a passport, do I need a visa, what is the currency, do I need a special plug for my cell phone?  
Because I enjoy researching and planning for vacations, I'm happy to look into the boring but important topics.  
Before I became a travel agent I often hired travel agents to help me book vacations.  They knew details that I couldn't find online.  They were able to get me rebates if the vacation price lowered.  They helped navigate insurance policies that I didn't understand at the time.  Sometimes I would book a part of the trip myself and other parts through a travel agent.  I often got theme park tickets and hotels through travel agents and booked airfare myself or we would drive.  And it didn't cost me anything -- in fact I usually got better experience and value with a travel agent than on my own.  
So let's address the question I posed in the title of this article -- How Travel Agents Make Money And What It Costs You?
As mentioned in the previous paragraph, it didn't cost me anything and often saved me money.  Occasionally there were service charges for changes or cancellations, but they were very reasonable, made perfect sense, and still the bottom line was better value than if I booked by myself.
Travel companies earn on average 10% of the pre-taxed price of the vacation.  Much depends on the type of travel and the standings of the agencies.  Let's say your pre-taxed vacation price was $7000.  If you book it yourself, you pay $7000.  If you book with a travel agent, you pay $7000 plus get services that will help you understand your destination, cancellation policies, insurance, receive cash back if the prices lower, and any updates on travel concerns.  The commission that supplies pay to agencies cover overhead mortgages, rents, utilities, staff, travel agents, training, administration, licenses, and more.  You really get a tremendous service booking your travel with a travel agent.  
Travel agents love the work.  Before you book your next vacation, ask your local travel consultant for a quote and see how it compares.  Your vacation starts the moment you email your travel agent.