The usual for a forebeam is to use a length of mast
companies will have specs sheets
giving a kg per metre spec for each section.
For a 50 foot boat you'd probably use a section that would weigh around 5 - 7 kg per metre.
The A frame won't weigh much, you could make it from either round tube, or spreader section. If I was doing it again, I'd integrate the forestay plate into the A frame. (I had a forestay tang welded into my forebeam.)
Between 5 and 10 kg for the A-frame with forestay plate. Probably around 10 kg for the wire, rigging
screw etc, and tangs.
The total weight is going to largely depend on the boat's beam - ie the length of the forebeam.