In accordance with DFARS 215.371-3 (a), if only one offer is received when using competitive procedures were used and the solicitation allowed at least 30 days for receipt of proposals the contracting officer shall--
 (1) Determine through cost or price analysis that the offered price is fair and reasonable and that adequate price competition exists (with approval of the determination at a level above the contracting officer). In these circumstances, no further cost or pricing data is required; or
 (2)(i) Obtain from the offeror cost and pricing data necessary to determine a fair and reasonable price and comply with the requirement for certified cost and pricing data at FAR 15.403-4. [I]f no exception at FAR 15.403-1(b), the cost or pricing data shall be certified.

Based on the above it seems prudent to only request certified cost and pricing data for those prices that the contracting officer cannot determine are fair and reasonable and not for the entire proposal.