Where there is a range of products or services the pricing reflects the benefits of parts of the range.
For example car washes; a basic wash could be $2, a wash and wax $4 and the whole package for $6. Product line pricing seldom reflects the cost of making the product since it delivers a range of prices that a consumer perceives as being fair incrementally – over the range.
If you buy chocolate bars or potato chips (crisps) you expect to pay X for a single packet, although if you buy a family pack which is 5 times bigger, you expect to pay less than 5X the price. The cost of making and distributing large family packs of chocolate/chips could be far more expensive. It might benefit the manufacturer to sell them singly in terms of profit margin, although they price over the whole line. Profit is made on the range rather than single items.