The short answer is that it's not just a website. The website is just the front of a large, complex project that involves many other things.
I have noticed how shocked people are when they hear how much custom software really costs. I don't know what you do for a living, but here's an example:
A family member hears you make software, ask you if you can create a website for his business for a friendly fee. Sure, you think. After reviewing his requirements, and deducting 50% because he's your uncle and you like him and want his business to do well, you give him a quote: 3 months and $10,000. He nearly gets a heart attack. What had he expected then? Well, a copy of windows costs less than $100. How could it be more than that?
It wasn't a parable about older family members being clueless when it comes to tech. People really can't imagine how a "new computer system" can cost 3 years and $90m to build, and are genuinely outraged, because it is so far removed from what they expect to be a normal or fair amount for a piece of software.
You pay a dollar for an app, $40 for a Sims game, maybe a few hundred for an OS and office suite, maybe $1500 for a fancy laptop. Sure you can imagine a 'website' might cost a few thousand, but _tens_of_millions_ ?? Surely, that is a disgraceful waste, right there.
I have noticed how shocked people are when they hear how much custom software really costs. I don't know what you do for a living, but here's an example:
A family member hears you make software, ask you if you can create a website for his business for a friendly fee. Sure, you think. After reviewing his requirements, and deducting 50% because he's your uncle and you like him and want his business to do well, you give him a quote: 3 months and $10,000. He nearly gets a heart attack. What had he expected then? Well, a copy of windows costs less than $100. How could it be more than that?