I would think it's hard to stay in business promoting Linux-first products as it is, and the higher price is because they know they will sell fewer units, and so they need to recoup a higher per-unit cost to functionally stay in business.
I agree that the price seems a bit absurdly high, but finding a quality Linux tablet of any type seems pretty dicey as it is.
EDIT: https://pine64.com/product/pinetab2-10-1-4gb-64gb-linux-tablet-with-detached-backlit-keyboard/
For example, this Linux tablet from Pine64 is more affordable, but with a Rockchip RK3566 it's just way underpowered compared to the N100, and that's over $200. Further, the Pine64 seems restricted to 64gb eMMC while the Juno Tab 3 can be upgraded to 2tb storage with its M.2 slot. I see no mention of an M.2 slot for the Pine64 Tablet. This genuinely seems like a more fully featured tablet compared to other available Linux-first tablets.