I've been reading the case study for Cisco systems http://gsbapps.stanford.edu/cases/documents/OIT26.pdf
and one paragraph under suppliers stated:

Summa Four purchased approximately 5,000 individual parts from 250 suppliers, 85 of whom
were new to Cisco. While the Summa Four acquisition was far smaller than the $4.6 billion
acquisition of StrataCom in 1996, Summa Four had a comparable number of parts and suppliers
to StrataCom, reflecting the complexity of the Summa Four integration process. Of some
concern was the fact that approximately 200 of Summa Four’s parts were sole-sourced, meaning
that only one vendor supplied each of those parts, which created a risk to cost and continuity of
supply.

i dont understand how the risk would be "cost and continuity of supply"? can someone help explain to me?