Johnston is the most expensive place in Greater Des Moines in which to rent an apartment, a new survey by RentCafe.com shows. In January, Johnston’s average monthly rental rate was $1,185, a 4.6% increase from January 2019. Urbandale had the lowest average monthly rental rate at $860; Des Moines’ average rate was $927. Nationally, the average monthly apartment rental rate was $1,392. See the entire survey.