What are the costs and processes for converting a Tourist Visa to an Education Visa in Thailand?

This is normal if you're talking about an area without many schools. They charge it because they can. In Bangkok it's unheard of because you can just go to the next school.

Data point: ProLanguage charges 15K for the conversion fee in-country (TR->ED). They do all the paperwork associated with the conversion. Another language school I know charges close to that. Then add tuition, books, and costs for each subsequent 90-day renewal depending on how long you want to be on the ED visa.

Normally you would go to Vientiane and get the Ed visa there and head back to Thailand on an Ed visa. Now because it is very difficult or impossible to travel to neighboring countries the easiest and closest place to go would be Sri Lanka for a visa run.

Hopefully the land borders will open soon.

Other option would be the bullshit volunteer visa, there are some places still offering. There is one major problem w this visa which is if you leave Thailand the immigration will not let you back in with this visa. So if you get the volunteer visa DO NOT travel outside Thailand. It is about the same price as the Ed visa but u don't need to go to classes

The cost of the school itself is going to be the main consideration.

Is it a genuine visa or one of those fake agency visas?

And it is ridiculously expensive. Make sure they don’t rob you. For a normal conversion of visa (e.g from TR Tourist to ED in country) the official fee is 1,900 baht. The number you are quoting should only apply if you are trying to do a conversion that usually cannot be done. Brown envelope money then. Would never do it / support this.