some agents (in Thailand)will help people get visas by faking the financial requirements. The e-visa system makes this difficult if not impossible. Many agents in Thailand will assist people to get visas without committing fraud, some agents in Thailand will cheat for profit. Some people act like the dishonest agents are not breaking the law. I assure you, if they are cheating on the financial requirements, they are. You're correct, its not possible to cheat the e-visa system. No agents pissing in the soup, so to speak.
there are several things going on here. if you use the onlne evisa system and provide proof of income, that's totally legit. other people are talking about using an agent, and faking the required funds. there are agencies that will do this, not all will. it is not legal, and while many have gotten away with it, it is a recipe for being arrested, deported and blacklisted if caught.