I’m 100% positive from experience doing VR in several non-iOS spaces that increased exploit value leads to fewer published public exploits, but! This is not a sign that there are fewer available exploits or that the platform is more difficult to exploit, just a sign that multiple (and sometimes large numbers) of competing factions are hoarding exploits privately that might otherwise be released and subsequently fixed.

As a complementary axiom, I believe that exploit value follows target value more closely than it does exploit difficulty, because the supply of competent vulnerability researchers is more constrained than the number of available targets. That is to say, someone will buy a simple exploit that pops a high value target (hello, shitty Android phones) for much more money than a complex exploit that pops a low value target. There are plenty of devices with high exploit value and low exploit publication rate that also have garbage security.

With that said, Apple specifically are a special (and perhaps the only) case where they are “winning” and people are genuinely giving up on research because the results aren’t worth the value. I just don’t think this follows across the industry.

[1] - https://www.urbandictionary.com/define.php?term=jailbait