Corruption is awesome in Thailand. It's so embedded in day to day business but yet the foreigner do gooders always complain. This agent business is a win win for everyone. I'd wager a very large % of foreigners in Pattaya rely on using an agent.
Oh and by the way the price in Pattaya for 90 day Non O and the 12 month extension with your own bank account is roughly 26,000 thb and in the 12-15,000 thb range for 12 month extensions.