The key is successful designs like the $20 LCR tester prototype. The Chinese have been going like mad on that with excellent results. For things like DSOs, the manufacturing process works against OSHW. Too much test gear required even if you have a finished design. The complexity threshold moves over time as test gear becomes cheaper.
Aside from assisting in the development, you're in a very good position to popularize designs by making small runs and selling them online. The way to measure success is the number of copies being sold on AliExpress and eBay. When things become available there, drop that device from the current active product list. Many of the Chinese merchants have very little money, so they have to be very careful about what they choose to manufacture. By providing sales figures on OSHW designs you will greatly increase the likelihood that a design will be copied.
I think that making money from designing OSHW is a pipe dream. However, someone who has designed a successful OSHW device can command better compensation in the employment market whether as a regular employee or as a contractor. IMHO the real benefit to OSHW is the reduction of the barrier to entry into serious EE work by reducing the cost of test gear for a personal lab. This results from giving all the profits to the manufacturers who all have to compete producing the same basic design.
Sun, IBM, SGI, DEC and HP spent a fortune on the workstation wars. Then IBM committed a billion dollars a year to Linux development and wiped them all out. Instead of $30-50K, workstations are under $5K, and the meager profits go to the hardware manufacturers. Yes, there are still $50K workstations. Microway sells s a very nice one with 1 TB of DRAM, 48 Xeon cores and several Tesla GPUs. It runs Linux.