It's not really true that they are "competitive" with bikes costing twice as much (unless you mean you can ride pretty much as fast and have as much fun).

On the gravel bikes, the Viathon is $2298 for a carbon frame and GRX 600 groupset. Specialised make the Diverge Comp E5 for $2100 with a (lesser) aluminium frame and a mixed GRX 600/800 groupset (better)[1], or you can upgrade to a carbon framed Diverge (with a Sram group set, so not directly comparable) for $2500.

[1] https://www.specialized.com/us/en/diverge-comp-e5/p/175289

Like Amazon and fakes/harmful products, you only have to get it right over x% of the time (is it half?) or more, in order to profit, at their scale.

From their logo "Quality tools and ridiculously low prices"

Seems they began selling on tools bought from bankrupt companies, and now act as a secondary channel for many "real" high end brands. (Ie they can sell overstock through this company without polluting their main market / brand)

I am going to guess they do more than just tools now.

Does that company have a history of building quality products? Do they support them when something breaks? What kind of reputation do they have?

When you buy a brand name product, you generally have a better idea what you're buying.

(Not to say there aren't some high quality generic products out there, but it takes a lot more time and research to find them. And sometimes it's just a gamble.)

Obviously, this implied value gets taken too far on both sides.