This here is an old listing of Highelf, one of the first modellers. It serves as orientation how many faces the meshes should have which get used en masse (so many people wearing a helmet at the same time for example). Unique items can go more up but shouldn't exceed it by more than 250%
- Normal helmet : ~500
- Full faced helmet : ~800/1000
- Body armor : ~1000
- Sword : ~250
- Special/Detailed sword : ~400
- Small axe : ~300
- Two handed axe : ~400
- Two bladed axe : ~500
- Lance : ~150/250
- Spear : ~200/300
- Shield : ~400/500
- Bow : ~100/200
- Crossbow : ~300/400
- Interior scene : ~1000
- Detailed scenery : <2000
- Medium scenery : ~700/800
- Small scenery : ~250
- Tiny scenery : ~100/200
Keep in mind that this is a list from 2006 and the game engine has improved a bit since then. It still serves well as a first orientation. You can also orientate on Native meshes which are similar to the ones which you want to create.