CoffeeQueen- The $5.50 fee is low but I don't think that would preclude you from getting a higher price in the future. You may not get $25 but you may get $10-$15. I've accepted a lower shop price before and was able to get 3x that amount when they needed someone.
Their pricing methodology doesn't make any sense to me as they start at $5.50 shop fee and they increment .50 at a time.
MF either sent an email or posted it on their site that accepting a shop at base fee affects whether or not your MAO is accepted and how big a bonus you get. They were quite open about the policy. And it sucks. It's counterintuitive because the cooperative, loyal shoppers get screwed instead of rewarded. I haven't done much with MF since they implemented their new website and when they stated their policy it made me less likely to take their shops.