Donor Fee

What is a reasonable donor fee for both first time and experienced donors? How much is too much?

So far I've looked at 3 agencies, and their fees are wildly different.

One agency seems to let their donors set the fee (and they are sky high), while another is strictly within ASRM guidelines, and another allows donors to select their fee as long as it falls within the ASRM guidelines.

So, what is the absolute limit you would pay an experienced donor?

Thanks.