It's been going on for decades. An agent will secure safe passage at airport and border. What we call VIP, or Fast track services. This is needed for repeat visa runners. The agent and the immigration officer both take a cut. There are thousand if not tens of thousands of foreigners using such services every year.
They are extremely strict indeed. You got accepted because it was your first bounce, the next bounce won't work. Btw, there no such thing as getting flag upon leaving Thailand, the flag is if you get denied coming back.
What Brandon is trying to say is that given that you lost points, but not much else, it's not worth fighting. If they had stolen 100k baht it's another story. The Thai way of dealing with such things suck.
The 5 years DTV is 100-125k baht with agent (if you don't have the proof of 500k for months in your account). It's the current on-going cost with most agent using their contact in Vietnam. 30k would be a scam, yes.
Such practice is omnipresent in America too. For example, the whole pet industry (Hills and Royal Canin), in America, make a fortune with deceiving marketing on their bag and can.
Also, if you are a repeat visa or visa exempt runner, you'll end up denied sooner rather then later especially since the new 60 days visa exempt which made most airport and border tougher. I got denied entry in Nong Khai after 10 years in Thailand (last December). So it took a very long time for me to get into trouble. I got in with an agent. You'll get in that way. You need to contact an agent and use fast track service to get in at Phuket airport for about 6-10k baht. It's basically a safe entry without hassle for people like you and me that will always moving forward be denied without a safe way in.