Have you seen the Pottery Barn Eagan Mirror? Love! The Lettered Cottage had a great tutorial that can be found here! We used Kevin and Layla's tutorial for this project. But make sure that you do your own measurements because 8" mirrors can vary in size. The ones from Michael's were just shy of 8 inches and the ones from Walmart were exactly 8 inches and that small amount of size makes a big difference especially if you have the bigger mirrors. The only thing we changed from their tutorial was we cut the back board slightly smaller and put molding on the side to hide the hardware in the back. Then just glued the other molding and a smidge of the mirror to the molding.
Total cost for the entire mirror was about $80.
Mirrors were purchased for $3 each at Walmart for a total of $32.
Molding for sides was about $10.
Skinny molding for insides was $8-10.
We used particle board for the back and it was $14 for two 2'x4' sheets. One sheet we only used a few inches of and can use the leftover for another project.
Liquid nails for mirrors was about $6.
Rust-oleum metallic paint was $8 a can. It only took one can and we sprayed behind the mirrors as well.