MK MG MEM 1-module RCBO are typically £14-16-19 on Ebay for boxed new.
TLC do them for about £23 off the top of my head.

Comes down to the brand, quantity & person and which wholesaler.

14 RCBO can be had for £250 which is not that bad - consider how much
14 MCB and 3 100A RCD cost :-)