哈，这次俺对你刮目相看了，原以为你就就会抓螃蟹，看来不是，这次关键的东西算你看准了。

通过州child support agency来申请修改抚养费用是可行的，而且都是免费的，查了一下，几个州都基本一样的政策。虽然不能直接修改court order，却可以在他们的帮助下完成各种paperwork，然后向当地court file。可以省掉这个律师费用。

下面是Washington state的相关规定：

9. Is this process different if the other parent agrees to the change in advance?
When the Washington State Division of Child Support is taking the lead in pursuing an order of modification, the
same basic paperwork is generally required from both parties whether or not the parties agree with each other or
not.  However, if both parents agree, this generally makes things easier and faster.   A modification of either a court
order or administrative order can generally proceed without a party needing to actually be present, particularly if the
parties agree.   
10. Does it cost anything to try to have my order changed?
If parents ask the Washington State Division of Child Support to initiate the order modification, the requesting party
does not have any costs to pay.  If a parent petitions the court directly for a modification, court filing fees will likely be required by the court and costs may be incurred serving the other party.

http://www.acf.hhs.gov/sites/default/files/programs/css/wa_cs_order.pdf

Wisconsin state 也有类似的规定:

http://www.acf.hhs.gov/sites/default/files/programs/css/wi_cs_order.pdf