:P
Someone is already selling a cheap Chinese card pen drive with bitcoin logo for 20 pounds..right OP?
Real cost of this pendrive without logo is 10-12$ maximum.
These are manufactured in the UK. They are higher quality then the Chinese ones and come with much better support and warranty. If you want to buy something that is cheap and will break within a month then Alibaba.com is your friend.
As a member who has experience in dealing with PCBA/COB/UDP and other integrated NAND orientated memory devices I initially came here to defend OP in saying his costs were reasonable however slandering Chinese made products is not something I approve of. A have dealt with quality testing from both local and "Chinese" products and whether or not your card was assembled in the UK or not 9/10 the actual components (i.e the actual memory chips) are always made in China. Just because something is Chinese doesn't mean it's cheap and shit, sites like Alibaba and Aliexpress offer (in the interest of full disclosure) shit products to top of the line products it all comes down to what you are willing to pay for. Since the card is often used as a promotional item or for actual consumer sale it is quite cheap to obtain, the real expense here is the actual memory component, for 16GB i'd say OP is making anywhere from 1/2 to 2/3 profit, depending on the volume ordered.