Probably less than you think.
The custom privacy solutions that MPS recommends vary fairly widely depending on a number of factors, most importantly the size of the area and the combination of treatment options required. A large multi-story project is typically around $2 a square foot. While a small office of less than 5,000 square feet can't benefit from the same economies of scale, MPS alone specializes in affordable privacy solutions for small to medium-sized organizations (try getting the other guys to even call you back if you're under 10,000 square feet!).
For example, a 100,000 square foot floor minus restrooms, stairwells, mechanical rooms, and break rooms might only have 80,000 square feet that require treatment. So for a project this size start the investment estimate at $80,000. Now let’s be conservative and estimate you'd recover 5 minutes per worker (studies regularly show almost 3x that). The system would pay for itself in less than a year and could provide an ROI of more than $400,000 over 5 years.
Considering the benefits of better visual and acoustic privacy, most organizations can't afford NOT to invest in a privacy solution.