I burned through pretty much all my upgrades to get 3 of the 4 caches and managed to get Jean on the 3rd. It feels super carrot-on-a-stick, but at the same time it's not the only way to get her as you can use collectors tokens. Of course, I don't have anywhere near enough of those so these caches seemed like the only remotely possible way I'd land her anywhere in the near future.