As mentioned above, contact local clubs and see where the members buy their fuel, you may at least find a LHS that gives club members a discount.

The other thing you could do, which would get the price down even more, is get several club members together and do a large fuel buy once a year. If you tell your LHS you want to order 10-20 cases of fuel, they might give you a much larger discount. If you live near a fuel manufacturer, contact them about buying it by the drum (55 gallons each). We are fortunate enough to be located near S&W Hobby, a fuel manufacturer, so my club typically buy 2-3 drums of 15% airplane fuel from them per year. Members bring their own containers and we distribute it on set days at the field. This year the club purchased the fuel for about $9 a gallon, and members paid $11 a gallon for it.