Fair does, if you can't afford it you can't afford it. Respect to you for finding the money to do everything else. You're quite right, it would be £300-500 you don't
have to spend.
My points really were (a) it's a lot less
extra than maybe you thought and (b) the training wouldn't be a waste, even if the priviledges would later be later superceded by those of the IR.
Most people don't bother. I'm glad I did.
I would add that, if you do decide to do it, make sure you get an IR rated instructor. An IR renewal examiner is even better.