Larger that what? It's Cape Gauge - 3ft 6in - the British colonial gauge of choice where difficult terrain was concerned. Most Sub-Saharan countries were at one time outposts of the British empire, and got Cape Gauge as a result. So did mountainous NZ, for obvious reasons, TBH, the terrain is suited to it, but Australia mostly [99.9999999% empty] went its own way, with a variety.
Oddly enough, Japan is also mostly Cape Gauge [the Shinkansen is standard gauge], but that is because the railways were set up by the British, and used British-built locomotives.
As for narrow gauge locos costing less than standard gauge, this is true of the smaller narrow gauge locos that we see in Wales and other places [you can still buy a brand-new Hunslet Quarry-class loco for less than £150K], but the Red Devil' is simply a full-size loco with the wheels a mite closer together. Bigger than ANY loco that ever ran in the UK apart from the LMS and LNER Beyer-Garratts.
How about this loco? Cape Gauge and quite large.
tac
OVGRS