For my plasma cutting and post processing project, I decided to cut and finish a diamond that had my initial in the middle of it. This is the finished product. 

First, I plasma cut the metal. I chose aluminum because aluminum proved to be better when cutting out some of the more detailed parts of the letter F. Dr. Wettergreen helped me to mess with some of the female and male cutting for this, since the inside of the diamond is semi-intricate. This is what they looked like right after being plasma cut.
Next, I had to decide on what kind of processing I would do. I knew I wanted to do an inverted design with colors and for the insides of the diamond to be different colors, but I also wanted the surface to be smooth. In the end, I decided to use the angle grinder to get rid of some of the leftover metal, raster and sand some of the edges to make the letter more defined, and to sandblast before I spray painted.

This is a picture of a diamond after using the angle grinder.

This is after being sanded and rastered.

This is after being sandblasted.

Lastly, I spray painted. This ended up being really difficult and annoying because of the design I wanted. I spray painted the diamonds red first, covering the parts I wanted to be black with tape. This ended up looking pretty good, except I had to spray paint again because some of the spray paint came off when I took off the tape. When I spray painted it black, thats when I started having issues. When I put tape over the red parts and spray painted the diamonds black, the black would still get on the red and when I took the tape off it would take off chunks of the red spray paint. In retrospect, I should have waited longer for the spray paint to dry. I put a clear glaze on both diamonds, and once again, this is the finished product.
Estimating how much it goes, I had to think of material cost, machine cost, and labor cost.

Aluminum costs $21.98 for a 3×3 ft. sheet at Home Depot. I also used red and black spray paint and a clear glaze. In Home Depot, a can of red or black spray paint costs $3.97. As for the glaze, it costs $4.31. A set of rasps costs $9.97. This comes down to $44.20 for materials.

For machine cost, the machine time usage for the plasma cutter and sand blaster can be calculated by the cost of a membership for a workshop. The cost is $125 per month. This equates to about $3.67 per hour. I used both machines for about an hour, so this would cost $3.67.

For labor cost, I was making a custom piece and decorating it myself, so I would pay myself $20 an hour. I worked in this for about five hours, so $100.

Altogether, the costs of these diamonds would be $147.87.