I once had a client who called me in to help figure a very basic bathroom remodel. They had a limited budget. I told them we could help them get what they needed within their budget as long as we stuck to inexpensive finishes and fixtures.
The next thing I knew the clients wanted to add finishing a portion of their basement. We went through the exercise of design for both the bathroom and basement, keeping things simple for a low budget project.
It wasn’t until I delivered the renovation estimate that the clients broke out into a sweat and told me they had expected me to stay within the budget of that very first ball-park number, the one I gave when the project was for the bathroom only. I had assumed it was understood that the cost would increase as the project scope increased.
Sometimes what you think is obvious is not so clear to someone else. I learned it’s best to communicate, put it out there, state the obvious, never assume.