Thanks for answering the inquiry. And sorry for not following up. I have been working and this bookmark really sat all the time in a corner.
Anyway, I came up with some what similar solution but more like a ready made solution with many associative problems. Because I had no better alternatives. Let me give a description.
The meter I had to choose has the flow range from 0-650 liters of diesel per hour. Plus it had to vibration shock resistant, magnetically sound working, water proof, must consider the counter precision after at least 0.1 million liter circulation, must be considerably small sized to fit the installation location.
Very few can manage those points in reasonable budget. the range that most closely works for me was $300-$600 USD meters, mostly produced in switzerland based company aquametro. Another company offered they can also manage the criteria.
These meters involve simple structure of pd meters which you can produce for fur less and improvise your own customized meter. The biggest drawback was the precision after 100,000 liter circulation limit.
As I was working with diesel flow, filter management was also important.
So I can say from the little search and discussion with professionals, that while choosing a meter, one must take consider the application criteria and the materials involved. For most cost economic decision and plausible application criteria, you might need to improvise over the existing products.
And once you can figure out what is actually needed, you can mass manufacture it in China or anywhere you find it easy for around below 50 USD. But will need rigorous testing. Meters are one of the oldest in the list. But for the leading manufacturers already worked on R&D for product development you must weight between the options. Must not compromise the quality or time/money.