Can anyone tell me why the 'value paperback' works out at more expensive to produce than the premium paperback? When I use the book cost calculator for the pocketbook size the value paperback is £2.80 per 100 pages and the premium one is £3.05 per 100 pages. However, when I type in 250 pages into the field, the premium paperback generates a cost of £5.30. Do the same for the value paperback and the cost generated is £5.80. A 'value' paperback?'