A lot of actors (especially older ones) will do work in films with extremely low budgets, either because they're doing it as a favour to someone, or because of things the film may have a number of younger actors/cast from various film schools that the actor may have links to*.From the emerging reports it would seem that this set was not typical; I would have thought a film featuring Baldwin - could afford realistic replicas and cgi?
There are countless low budget films with one or two recognisable names, or films that actors have done that are very outside their normal fair that they've either done for a change, or because they think their kids/grandkids would like, let alone the ones where there is a high profile name used in all the marketing but that person is only on screen for a couple of minutes and maybe 3 or 4 lines.
Basically seeing a "big name" involved in a film says nothing about it's budget.
*Some see it as a personal obligation to help newcomers get the same sort of breaks they themselves might have been given, Robert Heinlein used to refer to it as "paying it forward", you help someone with no expectation they'll pay you back, but in the hope they'll do the same to someone else in the future.