Which monolingual (classical) Latin dictionary?

I’m not sure if such a thing exists as described in the thread title, but I’ve been meaning to pick up a proper Latin dictionary for some time now, and seek recommendations.

Are there any monolingual dictionaries which are affordable for a private individual of modest means?

Does anyone have personal experience with any such dictionary?

Does anyone wish to challenge my assertion that foreign languages are best mastered (not merely acquired) with the aid of such a tool? If so, on what grounds?