I believe ours is about 2" which seems perfect for it, at least in our kitchen.

Cabinets are sold in 3" dimension changes, so 3" is the usual measurement used. But, what looks right will depend on several factors including cabinet style, overlay, sink choice, faucet choice, and window/no window behind the sink.

Mine is 2-1/2". But I have a farm sink that's also pulled forward of the bump out. If you're doing that, mine comes to 5"

Thanks for the reply everyone, I believe I'm going to go with between a 2 1/2"-3" bump out.

I talked to the fabricator and was told on a 36" cabinet a 3" bump out will cost another 1.8 sq. ft so that's $180.00 based on my layout.