single buyer - takes advantage of sellers  

• oligopsony - market w/ only a few buyers
• monopsony power - lets buyer pay less than market price for a good
• marginal value - additional benefit from purchasing another good
• marginal expenditure - additional cost from purchasing another good
  • E = expenditure = P(q)q
  • but P(q) in this case set by supply curve, not demand curve
  • AE = avg expenditure = P(q)
• quantity bought found at intersection of demand curve and marginal expenditure
  • price found by dropping down to corresponding price on supply curve

• demand
• supply, avg expenditure, P(q)
• marginal expenditure
• p* = market price

degree of monopsony power - depends on # of buyers, interaction between buyers  

• fewer buyers >> supply becomes less elastic >> more monopsony power
• buyers compete less >> more monopsony power
• more elastic supply >> markdown (p-p*) will be less

surplus - works out just opposite of monopoly  

• deadweight loss from smaller quantity desired by buyer(s)
• producer surplus lost >> increase in consumer surplus