Adding on to this: people overestimate their own expertise.

Very much 4

We wanted to get an engineer to audit something we set up, talking like 1 hour phone call, maybe 1 hour of work beyond that if something needed to be adjusted

We wasted like 4 hours on the line with different agencies (talking to sales people) who wanted to connect us with a DIFFERENT agency to do the actual work, who wanted us to sign a 3 year service contract.

Like no, "please just let us talk to one of your senior engineers and bill us $500/hr for his time"

#1.

Don't you just know it?! I work in media and I have pitched commercial projects to business executives many times only to see them completely choke on the costs. They say things like "Can't we just film the commercial on an iPhone, I see that on YouTube all the time?" FFS. I'll be like "Sure, we can. What's your budget for that? You realize I still have to pay the cameraman, the makeup artist, the writer, the producer, the director, the gaffer, and the talent. Do you want music with that, too? Oh, you want a Credence Clearwater Revival song in the background? That'll cost you."

I'll pull out some sheets explaining what they see on YT that they think is so cheap... I mean, sure, it's less expensive than other options, but crew and talent gotta eat and pay bills, too.

People have no idea...

The experts don't exist yet

This is something that people often don't know about. For certain things there can actually be little to no experts. One example, ski lifts. There are only a handful of people in the entire world who know how to splice together ski lift cables.

A more concerning one is nuclear engineers. There's been such a stigma against nuclear power that the amount of people who know how to build a nuclear reactor has fallen to incredibly low numbers. Also, the US had to reverse engineer some of their own nuclear weapons because the people who built them all died and the knowledge of how they were built died with them.