Generally speaking if a specific product sells a lot, it's safe to say it's a good indication that it's pretty good. And if you're wondering what those items might be, according to this recent report from B&H, here are some of the current Top Selling Products in various categories.
Top selling camera- far and away:
Sony Alpha a7 III Mirrorless Digital Camera
Top selling Lenses:
Tamron 28-75mm f/2.8 Di III RXD Lens for Sony E
FUJIFILM XF 100-400mm f/4.5-5.6 R LM OIS WR Lens
Sony FE 24-105mm f/4 G OSS Lens
Top Selling Tripod
Gitzo 100-Year Anniversary Edition Tripod with Ball Head
Top Selling Continuous Light
Aputure Light Storm LS C120D II LED Light Kit with V-Mount Battery Plate
Top Selling Studio Strobe
Profoto B10 OCF Flash Head
Top Selling Camera Flash
Godox AD200 TTL Pocket Flash Kit
Computers drives and storage:
Simple – 8TB for $139.99 WHOA!
WD 8TB Elements Desktop USB 3.0 External Hard Drive
Laptops:
B&H exclusive Lenovo 15.6" Legion Y7000 Gaming Laptop
and a close 2nd:
Apple 13.3" MacBook Air with Retina Display (Late 2018, Space Gray)