I currently sell on Etsy at duckandgoosedesigns.etsy.com.  Although prices are included with each of my listings there, here is my basic price list:

• Project using an existing design: $10
• Custom creation: $20 (although this is negotiable if you have a very small project in mind, such as a signature image for your email)
• Adding text to a photo: $5

There will be a small additional charge of $2 if you ask me to change the actual dimensions of an existing design, as that does require a somewhat significant amount of work to accomplish.  For example, all of my birth announcements are 5"x 7", but if you'd like it to be a 4"x 6", your total would come to $12 instead of $10.