I've been in three weddings in my adult life, MOH in one, bridesmaids in the others and have spent super varying amounts in each. here's the breakdown FWIW:
Wedding #1- low cost, beach wedding.
Bring-your-own-blue-dress: $50
Helped throw the bachelorette party: $150 (it was the night before the rehearsal dinner, so we stayed at the beach house the bride's parents had rented out for the bridal party)
Wedding/shower gifts: $150
Wedding was in NC, so not a big deal to travel to, and we stayed at my parent's beach house for the rest of the weekend: $0
total cost: $400
Wedding #2: big-budget "traditional" wedding
Bridesmaid dress: $300 (it was LulaKate, which i guess is a more "designer-y" bridesmaid line)
Bachelorette party (Charleston) travel costs: ~$400
Various gifts: $200
Travel to wedding (flew to MD, drove back with friends to NC): $150
Hotel cost for one night split 3 ways (stayed the other night in the bridal suite with other bridesmaids): $100
Total cost: $1,150
Wedding #3- low-budget, local NC wedding- I was the MOH:
Dress: $150
Bachelorette party- Nashville- (I helped throw it, but we stayed with cousin of the bride, so no hotel costs): $500
Various gifts: $200
Total cost: $~850