On my previous post about my As Tucas cuben dry sack, Alan made the understandable point that €40 (£34) seemed a lot of money to save 87g. I thought it would be interesting to look at some trade-offs of weight saved versus cost.
Firstly, taking rucksack liners, an Exped silnylon 50L liner costs £17 and weighs 72g. This is actually slightly larger than mine, so not a totally fair comparison. However, in terms of cost per gram saved it works out at 38p per gram. Of course, we must take into account that I rejected silnylon liners because of concerns over robustness.
If we take the normal gauge Exped liner (actually their XXL dry bag as it is a comparable size), then it weighs 110g (according to Amazon) and costs £15.50. The cost per gram saved of the As Tucas dry bag over this Exped liner is 23p per gram, which is better value.
If we take a quick look at tents, then we can compare the Terra Nova Laser Competition 1 and the Wild Country Zephyros Lite 1 as close substitutes. The Laser Competition is 194g lighter but costs an extra £135. Every gram saved in this trade-off is costing 70p.
If we take the Mountain Laurel Designs Duomid and compare the silnylon version with the more expensive cuben version, we find the cost per gram saved is 59p. I also looked at the comparison of the Gossamer Gear Mariposa and the cheaper Osprey Exos 46. in this case the lighter Mariposa will cost you an extra 27p per gram saved.
In the context of these comparisons, it no longer seems quite as extravagant to have bought a cuben pack liner. I guess the other thing to take into account is the cumulative weight savings. By chipping off a few grams here and there (albeit at extra cost), the extra weight savings soon become quite significant. In the end, it’s all a matter of personal choice. Everyone will have their own cost/benefit curve (to use a technical economics term!).