Many companies with competent engineers will from what I hear from a few in the industry only design on paper with no listening tests or comparisons to fine tune the sound
Mostly true except for their giga$ "statement/ trend-setting" products. Importantly, large companies are also very well equipped to c.a. design products that perform well "enough".
Remember:
*Tweaking is labour intensive and therefore expensive: it adds variable cost & R&D costs making the end product unmarketable (at the profit margins the corporation requires).
*Confirmed designer engineers are expensive and often work as consultants; having them on board full time would be VERY expensive -- if such engineers were willing, in the first place. Most are self employed or have their own consulting agencies.
*Small (garage) operations are often undercapitalised. So they lack the testing equipment and they have to revert to labour/ consultants. Since even this is expensive, they rely on and sell, the owner/designer/etc's design experience and tweaking "knowledge/art".
When such a company is small (employing 1-2 part-timers, the husband & wife, etc) they can indeed offer bang for buck. When they get larger, operating costs go up and some/many of them can no longer offer the same bang for buck as readily.
At least, the "entry fee" to this market is low: anyone with knowledge and understanding CAN come up with a product that MIGHT sell. Hardly so if it were a car, for example.
OTOH, the hi-end market is too small to attract mega investment in synergies & manufacturing optimisation that could give better bang for the buck. Compare to the automobile industry for example: a Merc containing 20-30000 parts & heavy R&D sells for the same price as a pair of big Kharma, etc.