I have a friend who is interested in answering the same question and we've discussed ways to gather those kinds of statistics but we don't really have any definitive answers.
Pet chinchillas are normally bred by hobbyists and made available to their local markets by small businesses. Some markets are privileged to have larger chinchilla fur ranches producing larger and higher quality chinchillas that keeps the overall quality of the stock up in the region but they'll usually sell pets as well. Some breeders just breed for quantity and this usually results in terrible genetic defects that don't show up until months after the pet is purchased. Usually these breeders cater to pet stores although some pet stores really do care about their sources and quality.
Between all those sources I would think the numbers are in the hundreds of thousands of pets overall. We are always looking for ways to connect breeders to good information and looking for ways to grow the market. I am seeing more chinchilla products being made available over the years. Unfortunately there are many products that are dangerous to chinchillas and could be causing poor health and early deaths which could potentially destabilize the market. The good news is I'm seeing a rise in the availability of niche market producers who are making safe products and memberships in organizations that are bringing breeders together and promoting good practices.
Overall I expect the market is increasing overall as knowledge of chinchillas is growing.
