I can understand you see learning a language might be seen as cultural in some way, but normally the ED visa would matching this betterand the rule is you should get the visa for your purpose of stay.
Since you cannot see difference between 60 days and 180 days, I guess it is useless to discuss this. It has nothing at all to do with scam, different service means different price, you pay for what you get, no matter what seller had to pay for it.
But you are in good company, even the president of the US does not understand basic principles of economy and mathematics.
DTV is certainly not the only visa you can get when you are over 49, because non-o retirement starts at 50.
DTV is not an education visa, so your remark "Learning is learning" is totally meaningless here, DTV is for soft power and remote work, scuba diving also has nothing to do with soft power,
The fact that some embassies did approve thai language as soft power does not mean it really is a valid soft power item.
let me try with the most simple example I can think of right now. When I transfer and exchange money the fee is higher when the amount of money is higher. Everybody sees this as perfectly normal, but for the bank, the cost of transferring the small amount is exactly the same as for the large amount.
I think you don't know how a borderrun works, they might not stamp your passport themselves, but they take care that IO stamps your passport without problems. What it needs to reach this might be different depending on type of visa.
When agents deliver what they promise, it is not scam, but just expensive for a service you can simply do yourself when you fully comply with the requirements.