White wall tyres were caused by the fact that early automobile tyres were expensive to produce, and carbon black was used to vulcanize the rubber and make it more durable, but it wasn't needed on the sidewalls, as a result the zinc oxide rubber was exposed.

When blackwall tyres became more common, they were easier to keep clean and contributed to a premium due to their higher manufacturing costs. Nowadays, a white wall produced at the same volume as a blackwall will be less expensive, but they're made in much smaller volumes, hence the higher cost nowadays.