We've had a little time to work with Royal Mail's price increases and thankfully there is some silver lining.
The cost of sending one pack of coffee has gone up by 20p. However, because Royal Mail have also increased the threasholds for the next weight bracket, sending two packets of coffee 1st class now costs exactly the same as it does to send one packet (£2.70).
So to summarise, it's much more cost effective for customers to buy two bags of coffee at a time, rather than one.
Hope that helps