That is interesting, and some might find it convenient, for a price. I checked several common parts I think are stocked by most repair shops and found all were 4-8 times more expensive than quantity 1 pricing from other distributors such as Digikey. The reason NTE/ECG was often used by shops was due to having it available from stock at local suppliers.
For example Mouser and Digikey has the ubiquitous NE5532a low noise opamp for about $1 and Arrow has it for $0.30 but the cross for NTE is NTE778a for $4.38. I used them when needed if for some oversight, I was out of stock and needed one in an hour, the extra $3++ was worth it to get one in hand immediately. That was the benefit of replacement types like the old HEP Motorola, RCA SK's or Sylvania ECG, a small number of separate stock numbers were needed so local suppliers were bound to have it.
Back a long time ago, the regional distributor for Motorola gave me a nice metal bin system stocked with HEP semiconductors and the field salesman would drop by once a week or very 2 weeks and take inventory and charge for those used. Sure they cost more, the difference was gladly paid since it was my penalty for not having a part in stock, when the unit needed to repaired RIGHT NOW. I doubt anyone begrudged NTE or others for higher prices when needed from local stock. Needing to order and get delivery 4-5 days later, makes it a losing proposition to use them since the other on-line distributors are so much cheaper and efficient for 3-4 day delivery.