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.
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