I would put the value of the upgrades (perfect fortitude and sundering) at around 250K, and the base swords at 150K and 100K respectively (for req 8 and req 10). So I think you can sell the first sword for around 400K and the second around 350K.
A lot of people prefer swords that are not pre-modded, as they prefer statistically superior mods like vampiric or defense over the more expensive and flashy mods like sundering or fortitude. Some people would be really upset, in fact, that the most expensive mods in the game have been attached to swords that are not the most expensive base in the game (the most expensive being 15>50).
I think you could definitely get the amounts I listed above, though, even in a dramatically changing sword market.
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