The Sweet Spot DSLRs...

Back in the 2000s, when full-frame sensors and all the various tech that was packed into full-house pro bodies from Canon and Nikon made them eye-wateringly expensive, both manufacturers produced a line of cameras that used rugged and weather-sealed bodies combined with APS-C crop sensors and a slightly less-than cutting edge feature set.

They wound up getting called "prosumer" bodies, but cameras like the Nikon D200 or the Canon EOS 40D were as often as not used by professional photogs and serious amateurs who did photography as side gig and couldn't justify a $4,000-$5,000 pro body.

A Nikon D200 with battery grip mounted.

As sensor prices dropped and the full-frame craze spread, these cameras kind of lost their niche.

Starting with the EOS 60D, Canon's two-digit crop sensor cameras lost their metal body shells and weather sealing, with the pro-grade crop sensor torch getting passed to the then-new 7D, whose single-digit moniker made no bones about its target market.

Nikon let the D300S linger unchanged for years and actually abandoned the category for a while until the D500 debuted in 2016. 

I really like these on the used market because they're great values and built like tanks.