GMAT Sentence Correction (SC) | While larger banks can afford to maintain their own

While larger banks can afford to maintain their own data-processing operations, many smaller regional and community banks are finding thatthe cost associated with upgrading data-processing equipment and with the development and maintenance of new products and technical staff are prohibitive.

A. cost associated with

B. costs associated with

C. costs arising from

D. cost of

E. costs of

Idiom : associate with. Between A and B ,why A is wrong? "cost associated with upgrading