Look for someone is willing to work with you. Watch out for deals that are too good to be true. You want your cake to not only look good, but taste good. Bring photos or sketches when meeting with your cake designer. The more info you bring the more you will get out of the meeting.
Some decorations cost more due to the time involved.
If you want handcrafted sugar flowers, they take time and skill. Refer to the page on The Art of Sugar Flowers. This page will give you a clear idea what goes into handcrafted items. Look out for hidden costs. Make sure to review all costs associated with the cake.