As a benchmark, for the extra protein granola, FUEL10K Protein Boosted Chunky Granola - Chocolate Loaded will be used which is priced at £7.45 for 1kg.
The regular granola is ASDA Simply Granola which is priced at £3.00 for 1kg.
FUEL Granola Nutritional Values:
100g of FUEL Granola = £7.45/10=£0.745
Therefore 75p=15.1g of protein.
Asda Simply Granola Nutritional Values:
100g of Asda Granola = £1.50/10=£0.15
Therefore 15p=10g of protein.
If you was to buy 75p worth of FUEL Granola, you would get 15.1g of protein.
If you was to buy 75p worth of Asda Granola, you would get 50g of protein.
If you was to buy 100g of FUEL Granola, you would get 15.1g of protein.
If you was to buy 100g of Asda Granola, you would get 10g of protein.
ASDA Granola Protein FUEL Granola
15p = 10g = 50p
The results are clear based on protein alone. It is more economic to purchase basic granola than protein boosted granola and eat a little more to get the same amount of protein. However, if you're trying to limit the amount you eat, its more effective to purchase protein boosted granola, than ordinary. Its worth noting that this only factors in protein and not energy, sugars, salts and so on. You should evaluate these factors too before making a purchase, but on protein alone, its more cost efficient to buy basic granola.
Summary:
If you're watching the pennies, its more efficient to purchase basic granola and eat a little more to get the same amount of protein.
If you're trying to limit how much food you consume, its best to purchase the protein boosted granola as there's a greater ratio of protein grams to serving grams.