If you plan to use them for wedding centerpieces, I might also suggest offering them as favors afterwards. This way, you're not stuck with a lot of them at the end of the day. Also, their double purpose will cut down on costs.
If you're looking to buy in bulk, I suggest doing your research. This trio at Home Depot runs about $16:
You can buy 12 small succulents at SucculentsGalore (ETSY) for $36:
Green Wedding Shoes has a great intro into Succulents... Check it out!