Here I will list ranges of prices I detected while trading in various systems.
I also will list the best stations for buying items at those stations.
Please keep in mind prices may change overtime, but I assume theese stations keep their prices relatively stable around those amounts

Medicines (price range 20 - 60)
BUY:
(Maru) FIL station: 20
SELL:
(Tega) Cayeux: 60
(Tega) Port Crawford: 60

Medical supplies (price range 35 - 140)
BUY:
(Tega) Sterling industrial: 35
(Maru) FIL station: 35
(Tega) Narail industrial: 35
SELL:
(Leo) Columbus: 125
(Leo) Lago: 105
WARNING (BEWARE due to a ?bug? a price might be -10):
(Leo) Prefect outpost: 140
(Leo) Penitent: 140
(Leo) Crassus: 140