Quoted from DakotaMike:

Historically, pinball designers DON"T get any royalties or residual payments. For instance, Brian Eddy talked about how he sees no money from the CGC Remakes. Now, I don't know specifically how it works at Stern, but I would highly doubt that anyone who worked on GB would see additional money for a Vault. Only the licensor would get any extra cash.
It seems unlikely to me that Gary decided to cut his designers in on cash royalties, when that hasn't been the historic precedent, and when he was the only game in town for over a decade.

Quoted from seenev:

I think that's going against the consensus here.
I work for a company that makes royalty management software. I don't know anything about Stern's contracts, but I would guess they aren't doing any kind of per game royalties. For one, they're probably not a big enough company to justify the overhead of processing those kinds of royalties, or even if they are, they don't strike me as being organized enough. I also think we'd be hearing more solid production numbers for each game if royalty statements were going out to any stakeholders.