Why isn't the Garmin Dashcam out yet?

What does "affordable" mean in your question?

less than $50?
less than $100?
less than $200?
less than $300?
a single camera or multi?
waterproof requirement (i.e. it is going outside?)

By far, our most common seller is the DieselBoss DB4 because it is sub-$100 with a card included, plus 1 yr warranty, plus live phone support. This satisfies the most common requirements, which are an inside windshield camera that is easy to use, has a viewing screen, has HD (720p, not 1080p) quality, good in low light without I/R beams bouncing off the windshield. I had to test a great many of them before I found what I needed to satisfy that niche reliably.

Elsewhere, they are also plentiful under various brand names for as low as <$25 (without SD card) everywhere from Ebay, to Amazon, to the truckstops, and other sites. It goes without saying that the cheaper it is, the cheaper the internals are. So the best rule of thumb I could give you there, is: call a phone number (preferably) or at least get an email response so you know there is a human you can speak to if you purchase it. Or ask the truck stop what the warranty and return policy is if you have a problem or don't like the quality.