Im not really clear, but is it expensive to fit rather than the actual POLE being expensive ? The reason I ask is that we have a full bay window and used a curtain pole & it wasnt expensive;
We got a carpenter friend to cut (mitre) the poles at the angles, cut a small slot into which he inserted a piece of hardwood, glued and pinned the join, and from there it was DIY. ie screw the brackets to the wall etc. There is no strain on the join as there are brackets on each side of it. Sorry if i'm making it sound complicated but it worked well and wasnt expensive.