Fair question, and it is the one every business owner is really asking the moment a web designer shows up: your grandson is good with computers, Squarespace is cheap, and the guy from church says he builds websites on the side. So why pay a professional? Here is the straight version, from someone who does this for a living: sometimes you should not, and I will show you exactly where that stops being true.
Some businesses are a page, and there is no shame in that. Your name, what you do, the towns you cover, a few good photos, your hours, your number. No booking, nothing to log into, nothing that has to talk to anything else. If that is the whole job, Squarespace and a free Saturday will get you there, and a sharp grandson will get you there for the price of a good lunch. Pay a professional to build a page and you have paid a professional to do a Saturday's work. I will tell you that to your face and hand you back your deposit. Go fishing.
The job changes the moment the site has to do something instead of just say something. Take a booking and hold the slot so two people cannot grab the same Saturday morning. Show what is actually open right now. Take a deposit and not lose track of it. Talk to the other tools you already run, your calendar, your card processor, the marketplace you list on, over connections that quietly change their rules twice a year. Hold customer accounts so people can log back in and see their history. Send the text that confirms the appointment while you are out on the water. The instant any of that is on the table, you have walked out of web design and into software, whether or not a single dollar ever moves on the page. Software is a trade, the same as yours, and it takes someone who works at it.
The catch is that a cheap build usually looks finished. The front of it reads just fine. The working parts underneath are often a stack of borrowed pieces nobody actually owns, wired together once and left alone, and borrowed parts wear out: one updates and breaks its neighbor, one gets abandoned, one starts charging a fee, and the booking form quietly stops sending on the busiest weekend of your year. The grandson wired it in an afternoon, meant every bit of it, and is now three states away at school. Nothing was built to be repaired, because nobody planning it expected to be the one repairing it. You find out it broke the way everyone does: a customer mentions they tried to book you and could not. None of that is a failure of effort. It simply was not built to survive a season, and a season is the whole reason you needed it.
Working software is only worth more than a page if someone keeps it working, and that is the part no cheap quote mentions. When the confirmations stop going out, or the payment link starts throwing errors, or the calendar sync slips a day, you do not need a forum thread and the maker of some borrowed part who moved on years ago. You need one person who understands the whole thing and picks up the phone. That is the real difference between buying a website and hiring someone. The website is a thing you own. The someone is a relationship that lasts past launch day, which is exactly when the thing you own starts needing attention. And I am not passing through. Hardly anyone here is truly native, so I did the next best thing and married one. Southwest Florida has been home longer than anywhere else I have ever lived, and I do not plan on being hard to find when your season gets busy.
If your business is a page, get the page, keep your money, and tell the grandson he did good work. If your business actually runs on the thing, if it books, charges, syncs, and remembers people, then you want it built by someone who builds software for a living and stays in town to keep it running. I have done exactly that for businesses that look a lot like yours: a boat-care company here got a real quote-and-payment portal, an airboat charter got a site that carries its own weight, a shop floor got a full working app to run on. That is the work a grandson cannot hand you and a template will not. And the care plans, from $60 a month, are the part where I stay, so the thing that does the work keeps doing it.
More straight talk: do you actually need a website?, is SEO worth it?, and do you need a social media manager? Or read the whole series.