OPEC works the same way as a union. They are both groups of competitors that band together to form a cartel, using similar tactics to increase the price of the product the sell. In one case, oil, in the other, labor.
OPEC is made up of oil producing countries and their combined output. They are extremely similar except that one deals in labor, and the other in petrochemicals.
One is big enough to influence the global market price for it's product, the other is small and localized and has effectively no influence on the going market rate for it's product.
On a local level? Maybe? But consider that the US workers of the most valuable car company in the world (by a factor of about 3)are not part of the UAW, so it's debatable at best.
Tesla is a tiny, tiny company. Tesla's market share is about 2.5%, or 14% when only looking at electric vehicles.
It's not even in the top 10 of car manufacturers by revenue. In fact it's only like 1/5th the size of the tenth place (Hyundai), or about 1/14th the size of the first place on that list (Volkswagen). It's not going move any car markets on its own, regardless of what goes on at Tesla.
So yeah, valuation is completely detached from (current) reality in this case, and Tesla is not a great example.
We could look at the biggest manufacturer instead, but I'm sure most people have heard of VW's union by now.