Production started

 10 of them for starters.

Very rough and ready, not sure yet how many I intend to make or about variants.

In terms of cost, these things are costing me virtually nothing. The card boxes I'm using as the 'spine' have served their purpose and are surplus to requirements. Which leaves card, glue, paint and time. All of these are already available except that I've bought some extra card. I can't really cost the paint - suspect my white undercoat spray will run out before these are finished meaning another trip to Halfords. For the card, costs about 25p. per building or less.