Berocca at Costco:
6 x 15 Orange for £14.38 (£2.40ea)
4 x 10 Boost for £11.38 (£2.84ea)
Admittedly I usually go for cheap the supermarket equivalents, but if you're Berocca loyal then this seems like a good deal.
Looking elsewhere and they are abut £4.50 for a box each, or 3 for 2 in some supermarkets which is still more expensive than this per box.