Cable spend should be a percentage of overall system cost IMHO.
No point in spending £100 on an interconnect and £100 on speaker cable that connects a £100 CD player to a £100 amp and to £100 speakers. The cd/amp/speakers simply are not capable of reproducing the level of detail required in order to tell the difference between those and a £50 or £20 cable.
Some systems on the other hand would clearly demonstrate a difference between those cables.
Audio cables are one thing, some of it is snake oil for sure but it is not in the same league of snake oil as £1000 kettle leads and £500 wooden knobs!
Butuz