Propane Exchange Pricing in the Chicago Area

Last night, I went to Home Depot in Evanston for a quick propane exchange. Out of curiosity, I called a few other places this morning to get their prices. Here is a summary (all prices in US$, not including about 10% sales tax):

• Clark Devon Hardware:
• CVS:
  
• Home Depot:
• Lowe's:
  
• Menards: 17.82
• 7-11:
  

I think it would be cool if Chicago Gas Prices included propane exchange...