That's a loaded question without a clear answer. The simple answer: It varies depending on model, brand, condition and team.
For example, gloves... a pair of Bauer APX2 gloves, most can be re-sold anywhere from $80 (well-used) to $170 (new). BUT, it depends on what team (new condition): Capitals ($150-$180) or Ducks ($90-$120), and it also depends on who used them: Ovechkin (between $800-$1200) or average player (between $120-$150).
The two biggest factors will be condition and what team. Hardly anyone wants gloves with holes/rips and very few people buy all-black or all-red gloves.
Again, this is just for ONE model of a particular brand. Multiply that by every model (and color) offered by every brand times every player/team.
In short: If you're buying for yourself or teammates, then ask us for reasonable bulk prices on specific items (or watch Ebay, which is a good indicator of what sells and for how much). If you're buying for resale, don't. Market is already over-saturated and margins will be relatively small.