I seem to recall that a parallel runway was always a consideration in the original design of the new Brissy airport. That being the case why did they waste the $ on the cross runway?

It is a pretty old airport really, I'd say that the single runway catered for the lower traffic volumes of the time, with land set 'aside' for future expansion when traffic density dictated it. Haven't done too much research but my guess is the cross strip was a compromise between the airport budget and the convenience of having two runways capable of simultaneous ops. Mind you, the 14/32 has done it's fair share of work. Nothing like a little bit of converging traffic management in peak times.