Wood countertops that are 3"-4" thick looks great but can cost a lot and in many cases break the budget. Using a built up edge can significantly increase the thickness of a wood countertop without taking away from the look. It saves a lot of wood and in the process saves money. There is one draw back, the labor. It takes time to add this edge so in cases where the countertop or island top is small the added cost in labor can overtake the savings in material. For larger tops the saving can be huge though and in many cases half the cost.

At the ends you can see the book matched built up edge. This could be used as a design feature and not only a manufacturing technique.
There are stringers that run across the bottom of the countertop so it sets flat on top of the cabinet. The built up edge does not hang over the edge of the cabinets.

The underside of a kitchen island with a built up edge.

For this countertop the edge received a large format profile and we were able to hide the seam in one of the decorative beads.

This sapele mahogany kitchen island was made in the same fashion. It's 1-1/2" thick with a 1-1/2" thick built up edge making a top that looks a beefy 3" thick.