Having some first hand experience in the hyd hose and fitting world in both the industrial and aerospace markets I would say that there is not much difference between the cheap fittings and the high dollar Aeroquip types. Except for true AN or MS spec'd fittings. Nothing industrial is ever qualified for use in the air.
There is a good read on Air-Way's website providing a brief history of the AN to JIC fitting.
https://www.air-way.com/news/whats-the-d...-air-way-fit-in

Most of the companies in the states are using mfg sources with screw machines set up to pump out straight fittings (hose ends and adapters). Forged shapes come from companies such as Brennan Industries and are then machined at centers to be finished off. Hex bar stock (cold rolled or aluminum) can come from anywhere and fed into the screw machines in the states to be "Made in USA". The brand/mfg stamp is struck on the bar stock before machining. A single screw machine could pump out several mfg's parts just by changing the feed.

Take a look at the Earls site and even Fragola and look at the carbon forged shape pics. There is a BI stamped on the body. That is Brennan Industries. Based on the info on Fragola's site they run their own screw machines and possible cnc centers (for forged shape machining).

Companies such as Parker and Aeroquip have or had production plants in Cleveland, Maumee, and Van Wert OH and pumped out fittings for OEM, Aerospace, and Industrials. That may have changed since I left the hose mkt, but that was back in the early 2000's.

And for pricing on AN fittings...the supply chain group I was a part of supplied true AN/MS fittings to the Gov't and even Stratoflex for fractions of what they are going for on some of the aircraft supply sites.

And one hex past finger tight is all it should take to seal up a 37deg union.