Where would be the best place to sell PLEX in high-sec as of right now to avoid paying hefty sales tax fees?
JITA 4-4 Trade Hub
That depends on your skills and standings. The naked numbers for all New Eden you find here:
You can’t avoid sales tax fees, they are going to NPC, regardless of where you sell. Only way to avoid is a private contract.
Make a public contract… And see what cost you get …