I'm going to wander into a bit of speculation here. Bear with me.
First: I've purchased from both Jenny Wu at Docan and Amy Wan at Luyuan. They both are very trustworthy and I would recommend either of them.
However, the prices you are comparing seem oddly far apart. I just bought 8 of the 280Ah EVE LH280K late last year from Amy, and they were $126/ea before transaction fees. $193?! That sounds way high. Although I know nothing about it, Amy supposedly will also sell
matched cells, which will cost quite a bit more. These would be cells that have been tested for exactly (or nearly) the same internal resistance and capacity and matched on those characteristics. I think
@Steve_S has bought some of these matched cells from Amy, so maybe he can chime in here.
What Jenny at Docan cells are definitely not matched cells. They are all grade A new from the factory, but that is about it. Whereas Amy gave me capacity testing info and three different IR measurements for each cell, Jenny said she had no such information.
Anyway, I think your two quotes are for different things, and you are comparing apples to oranges.