Just have an analysis of these gigs worth $5 (basic package) in this category. You will realize, the average prize of both packages surpass $30. For example, one seller's package constitute ($5 basic, $50 standard and $100 premium). If the system weighs his average prize alone (through fiverr's calculation formula), his av. prize easily shoots to $30+. In addition to that, some of these sellers whose gigs are worth $5 are offering gig extras too, combined. That's why you see some $5 gigs on this category.
That's the final decision. Your gigs must be set at prices not less than what the system wants