What are the trade-offs of strictly following SOLID?

Strict SOLID adherence has real costs. (1) Increased number of classes/interfaces — splitting responsibilities creates more files, more navigation overhead, and more cognitive load for newcomers. (2) Over-abstraction — creating interfaces for everything adds indirection that makes code harder to trace and understand (Java enterprise patterns like the infamous "AbstractSingletonProxyFactoryBean" are examples). (3) Premature optimization — designing for extension before understanding what will actually change can lead to the wrong abstractions. (4) Performance overhead — polymorphism and dependency injection add runtime indirection. The pragmatic approach: apply SOLID principles where complexity justifies it. Simple scripts and small functions don't need DIP. Apply SOLID proportionally to the likelihood and cost of change.