Having everything static gets mundane quickly,
Having a dynamic pricing system of drugs is what i suggest, in terms of certain drug prices rising in cost at some points and being more cost effective than others for a while whilst others can reduce, and it rotates, Giving each racket some boost particularly the least used ones.
E.g: H Q and M has increased by 10-20% to sell to an NPC whilst W, L and C has reduced 5-15% etc and rotates around. Or can be limited to single drugs, like a dynamic market.
Having some announcement in rumours or something, or going up to the NPC and interacting with them will let them know like "Hey the market is quite saturated right now, I will be paying 5% less" or "Hey, got any [Drug]?! We're low right now and need some, we hiking the price up to sell by 10%!"
Moving NPCs:
Each NPC has a static location, it would be nice to have them move to different locations around their local area, or even around the map; this may make selling slightly harder as youd need a way to find them, but also puts NPCs in locations which may be risky, i.e in enemy turfs etc though this is in the case of moving them around the entire map (i,e W NPC moved to long tunnel parking spot, or C NPC moving behind TH2&3 alley way.
Giving these dynamics can help each racket out and give some spark to the RP, removing the very static nature and spice things up.
The timings of drug pricing increase/decrease and NPC locations can change up to the relevant staff members of course to find a good balance, but its a highly suggested feature