Is there an analogue industry where the product is semi custom for each delivery yet had economy of scale? The closest I’ve had first hand experience with is t

Is there an analogue industry where the product is semi custom for each delivery yet had economy of scale? The closest I’ve had first hand experience with is the B2B analytics buisnesses I’ve run, economies of scale in that case are achieved via standardization of parts of the value chain, but true product level economies of scale where never really in the cards nor achieved. I suppose the closest to that would be the promise of prefab but can see in the comments here that has not panned out