Do schools assist with soft power DTV applications and what are the costs involved?

The price of the visa is mentioned on the website of the Embassy you are going to use.

You need to apply for the DTV while being outside Thailand, the organization which you like to use is inside Thailand. Chance that they will go with you to do the typing and uploading documents in another country is slim, but you can always ask.

Normal price for the soft power DTV is 10.000 Thb

There is NO cheaper visa, there might be a difference in cost of education at a language school, cost education and materials at a cooking school, there are differences in price for medical treatment, pulling a teeth is cheaper than several surgeries.

Training Muay Thai with or without education differs in price.

Think by yourself that this DTV can be used for almost 6 years stay in Thailand.

IF you have to discuss the price before even starting, can you afford 6 years living without income from working?