Even in the US, which is first to file, your patent can be invalidated by published prior art that makes it obvious. The stuff made here video is a textbook example of an invalidating piece of prior art.
Bottom line, you don't always patent the whole device, sometimes just the small unique implementation details are valuable enough.
And so rather than litigate, roll the dice and potentially strengthen the patent's standing sometimes it's easier just to negotiate a deal with them.
Yes, it costs money to get a patent invalidated based on prior art. But: an amount that even a single person who stands to actually gain from having a patent overturned should have no problem with. You're asking the USPO to spend time redoing work, literally halting any other patent work they could be doing instead. So it's not a trivial amount, but it's also hardly a prohibitive amount if you actually want a specific patent revoked.
The AIPLA Report of the Economic Survey for 2017 notes that the typical patent infringement suit with less than $1 million at stake costs on average costs more than $600,000 dollars, while the typical patent infringement suit with between $1-10 million at stake costs on average nearly $1.5 million to litigate.
https://blueironip.com/what-are-the-costs-to-enforce-or-defe...
Costs for IPR or Post-Grant Review (approximate mean):
Through filing petition: $120,000.
Through end of motion practice: $300,000.
Through PTAB hearing: $400,000.
Through appeal: $600,000