In my experience, waterfall needs unlimited time and money. Waterfall fails hard when money or time are limited, in which case the likely outcome is that the head of waterfall will be massive and the tail will be rushed, so that one gets a design-heavy and rushed implementation with little or no testing and scant documentation etc.
A timeboxed waterfall with inflexible sculpted-in-stone time schedules are a recipe for burning in the ensuing deathmarch. The planning either cannot or will not anticipate all unknowns and/or the buffers dampening the impact of the unknowns shrink because of outside pressure. (What do you mean 8 months to make this thing, can't you do it in 2 weeks, haggle haggle, sold for 2 months; available time reduced by a factor of 4)
In contrast, (a theoretically ideal) agile or some other iterative method works fine if time or money are limited. The iterative nature allows for a cut-off after a sprint. Pull the plug and have a result of state-of-the-art at that point; of course the result then might not quite reach the viable dimension of MVP nor even resemble a product.