200g refill packs of Waitrose Gold Instant Coffee are £3.87 and on an 'Add 2 get 2nd half price Cheaper Item Half Price' offer.
These packs are also included in Waitrose Pick Your Own (PYO) offers
This means that if you buy 2 packs, you get discounts of £1.94 and £1.56, leaving £4.24 to pay. Obviously this equates to paying £2.12 for 200g / £1.06 for 100g
This is listed 100% Arabica, strength 3 instant coffee. It's not the best, but at the price it's good enough.