Please do not rely on getting on the SCJP 1.5 Beta. The Beta exams are usually only available to those who have passed a previous version of the SCJP examination. (I think I'm wrong on this, I just checked back though old posts on the 1.4 Beta and that seemed to be open to non SCJP holders)
As for getting a cheaper price for SCJP I think that this is perhaps possible via certain educational schools/colleges/universities. SUN also has been known to offer cheaper (or even free) certification events at computing conventions.
As for registering, it's not formally announced as yet. We all have to keep our eyes open for an anouncement on Sun's site or here in this forum (if we keep ourselves in Sun's good book )
Can you please provide more direct information about signing up for this *free* Tiger beta certification exam