It sounds like the higher fine is because of a failure to appear on the original speeding ticket. You may not like this advice but you should've reached out to a lawyer before you appeared in court - it makes it much more difficult to do anything now. There is no fee lowering - you pay the corresponding fine of what you were convicted for. In order to get a lower fine, you need to not be convicted of whatever carries that fine.
You could try finding a traffic court attorney to reopen the underlying speeding charge so that there can be an appearance made on your behalf and then, at that time, try and get the underlying charge dismissed so that the fine is reduced. However, it seems like you've already pled guilty to the underlying charge in court - is my assumption correct? If so, your best bet is to simply go back to court and ask for an "extension period" to repay the fine amount. Just know that also carries a fee in order to implement....should the judge choose to provide it to you. I wish I had better news for you. Good luck!
This is NOT legal advice. No attorney-client relationship exists.
I agree with my colleagues. It sounds like you have a failure to appear, and that is increasing the fine.
You should fight the case, either with the help of an attorney or on your own. Why just hand over your money to the government?