If you're trying to fuel your riding with the best energy gels, and you're riding a lot, the cost can very quickly rack up. Using the most expensive on this list - Maurten 100, which suggests you can consume four per hour - and riding for 10 hours per week. That's 40 gels per week (assuming you're only fuelling with gels, of course). At around £2.50 / $3.50 per gel, you're looking at £100 / $140 in a week. Sure, you're probably not going to only fuel with gels, but the principle remains the same... gels can be expensive!
There is a limit to how many carbohydrates your body can process per hour so the simple maths of it is that the more carbohydrates you get in a gel, the fewer you're going to need to consume. Therefore, higher per-gel costs where there's also a high carb content might actually be better value for money.
Therefore, if we're purely focussing on the ratio of carbohydrates per price, things become pretty straightforward: If a gel with 20g of carbohydrates costs £1/$1, and a gel with 40g of carbohydrates costs £2/$2, the value for money can be considered equal.
In order to quantify this and make it easily comparable, I have calculated a G per £ ratio (Grams of carbs per Great British Pound) for each of the best energy gels listed above. To calculate this, I've taken the recommended retail price for the smallest multi-pack order available, which in most cases was a pack of six or 12 gels.
The value can usually be improved by buying higher quantities in bulk.