When comparing costs remember to include the effects of purchase-tax and import-tariffs.
Your $400 US-made receiver could have been slapped with a 40% import-tariff followed by purchase-tax.
Purchase-tax was a variable that could significantly distort apparent price: it penalised supposedly 'luxury' goods - what constituted 'luxury' was a matter of protracted legal wrangling [is a radio-with-a-built-in-speaker eligible for PT? Does fitting it with a BFO make it a utilitarian 'communications' receiver so no PT?]
Same went for radiograms - which were seen as 'luxury' items so attracting the highest rate of PT - so manufacturers started supplying 'radios' in big cabinets with a cutout to take a turntable but with the turntable not-fitted, so they didn't incur the punitive purchase-tax. After purchase, your local dealer would then offer to supply the turntable at a good [non-PT] price and fit it for five shillings.
https://en.wikipedia.org/wiki/Purchase_Tax