for relatively simple basic cards i charge $2. if a card involves more extensive cutting, layering, embellishing, etc, i charge $3. when you buy from a card shop, you pay at least that. also, just test the waters. set the price you want and see how they sell. when i first started selling, i charged $1.50-$2 and believe it or not, people told me i wasn't charging enough. people looking for a bargain are going to buy elsewhere anyway. those who appreciate hand crafting and art will be the ones buying. and when i think of some of the outstanding artists on this site, i would pay even more. i've seen work that i consider art worthy of framing.
hope it goes well for you.