The preposition that commonly comes before the word "cost" in English is "of." This construction is used to indicate the amount or value of something. For example, "The cost of the new car is $30,000." This usage is widely accepted in both formal and informal contexts.

The reason for using "of" before "cost" is rooted in the origin of the word "cost." Historically, "cost" comes from the Old English word "costen," which means "to pay." The preposition "of" is used to connect "cost" with the thing that is being paid for or the expense associated with it. This usage is supported by various dictionaries and grammar resources.

Data from the Corpus of Contemporary American English (COCA) further supports the prevalence of "of" before "cost." In a search of the COCA database, the phrase "the cost of" appears significantly more frequently than other prepositions followed by "cost." This indicates that "of" is the most common and accepted preposition to use in this context.

For instance, in the COCA, "the cost of" appears 1,724,972 times, while "the cost for" appears 614,745 times, and "the cost to" appears 535,905 times. These numbers demonstrate that "of" is the most frequently used preposition with "cost," reinforcing its standard usage in English.