Hi I am trying to apply LL.M program online but there is LSAC registration for all official documents. it cost 185$ other than 75$ for uni application.
please suggest or advise some about this.
is it a must for ll.m. application today? how can i avoid it?

For most of the law schools LSAC registering is not a must, but most schools recommend it. Of course, 185 $ is not cheap, but you have to keep in mind that you will have to send Transcripts to several schools (mail can be expensibve too) and you maybe have to add money for ets sending you TOEFL scores. Moreover, Universities from outside USA often do not write Transcripts. It can be hard to get 5 or more Transcripts, but that is only a problem if you want to apply to several schools.
LSAC is quite easy because you only have to send your Transcripts and scores once and they distribute it directly to the schools you are applying.
But if you don't want to register at LSAC, it usally is not required. There are only a few schools that require LSAC registration. Look at the list at LSAC's website.

Good Luck