Consider usage, not just supply prices.
D003365:Costs and Cost Analysis; D003625:Data Collection; D004865:Equipment and Supplies, Hospital / Q000191:economics*; D005249:Fees and Charges / Q000639:trends*; D007250:Inflation, Economic; D008421:Materials Management, Hospital / Q000191:economics*; D011682:Purchasing, Hospital / Q000191:economics*; D014481:United States