It cost me about $15 to make. It's my original design.
The larger diameter tubes at the top, I call "bubble tubes." Each one is big enough to contain all of the fluid in the manometer. That way when things are out of balance, the gasses can bubble through the fluid rather than sucking it all into the engine. (The fluid is automatic transmission fluid.)
More pictures:
http://alphadogcustoms.com/BuildBlogs/manometer/
The "J" bolts with the wingnuts are to restrict flow and steady the pulsations. Without something to restrict the flow, the fluid will be sucked into the engine in spite of the bubble tubes. (The bubble tubes could easily be a larger diameter, and it would be a design improvement.