Convey your heartfelt thanks with a touch of the Fat Penguin and his Bag ’O Gratitude! :)
Please note that the listed prices on the RedBubble shop exclude shipping costs and tax; these are default settings. To help you understand better what exactly you are paying for (e.g. shipping, tax, per-unit prices, etc.), I’ve prepared a short document that gives you the breakdown of the price inclusive of other costs; the URL can be found below.
Also, on a per-item basis, the shipping costs and tax are significantly lower for larger purchases. For example, if you’re in central London, ordering 1 greeting card would cost you £2.98 whereas 5 would cost you £1.71 each (that’s almost 100% per-item discount!), and so on. This information is all included in the document, which you can download here