I agree, as so often, with Drew.

I’d add that if you rewind to the 50s and 60s, the Original 50 (including its British-market cut-price version the 50E) either matched or undercut the BSA Airsporter and was definitely cheaper than the Webley Mk3, while offering similar or better performance and good quality.

The 35, though not well-remembered now, was in the same bracket as things like the Webley Falcon, Hawk, and later BSA Mercury, but just better.

And the 1978-onward 45 was a decent and cheaper competitor to the FWB Sport (best sporter of the 70s) and the slightly later HW80 (although many 1980s “12 ft-lbs” 80s actually came out of the box at 16-18, hence their “very parfull” reputation).

Diana were hugely helped in the 70s and early 80s market because they offered everything from cheap tinplate things, through boys and youth rifles, to adult sporters, and both entry level (model 6, 66) and high-end (10, 75) 10M match stuff. Something for everyone. No other maker did, ever.

The 34 and 48/52 series did pretty well in the 80s and early 90s. (When introduced in the the U.K., the 34 was cheaper than the basic models of the Mercury, Vulcan, or HW35, less than 3/4 the price of an HW80). As Drew says, the importers rather lost interest, hiked the prices to eventually stupid levels, stopped the advertising, and generally screwed the brand.

By contrast, in the US, the 34 quickly established itself for two or three decades as the thinking-persons entry-level sporter and the 48/52 as the (IIRC, cheaper) rival to the full-fat HW80.