Hi again
I'm sorry I disappeared from the discussion. I thought I would get email notifications of new replies.

The technical solution has become more mature since September. It now supports humidity measurements. Radio range is much improved and testing will hopefully confirm support for altitudes of 7-9 km.
The weight is optimized to the point where 30 liters of helium should suffice. This makes a sounding very cheap as long as the electronics is recovered. We're looking into offering a variant for one-time use but haven't determined what pricing is possible yet.

As for alternatives, I don't see how a kite could measure winds and altitude is limited indeed. Results from a rocket would be inaccurate due to high vertical speed. In both cases, the payload can detach at peak altitude and take measurements while falling to the ground. That would mean the electronics still has to be retrieved some distance away.
A helium balloon is cheap but these other solutions would also work with Windsond. Approximate GPS coordinates of landing site together with loudspeaker, radio beacon and flashes of light makes it easy to recover.

We're now working to estimate the market to motivate production. In parallel, I'm doing development and testing. Your comments are valuable!

Regards
/Anders Petersson