Why The Disparity In Gas Prices?

Hi, Leslie Harris here, and on Sunday evening, I stopped at Costco in Oakbrook, and was really happy to get gas at $4.15 a gallon for regular. The very next day, I saw this: $4.05 at Speedway, at the corner of Fairview and Maple in Downers Grove.

Well, I was disappointed that I had paid $0.10 more just the day before, but also happy to see that prices are dropping.

But on my way to work today, I passed a Shell station in Aurora on Eola Rd. that had it for $4.48! I understand that Shell is more expensive than Speedway or Costco, but this seems a little ridiculous.

And the rent/real estate in Downers Grove and Oakbrook is generally higher than Aurora, so why are these prices are varying so wildly?

Anyone know? Let me know in the comments.