The simple answer is price in lots of risk for the risk that you identify ... and state how much you have added in for each risk e.g. due to the vague specification, I have priced for a Rolls-Royce solution with high quantities. Hopefully, that forces the PM to clarify what it is that is wanted, and refine the risk profile through stating assumptions.
However, Ideally those putting together the quotation and evaluating it have these discussions upfront before the Contractor goes off and does the quotation.
However, Ideally those putting together the quotation and evaluating it have these discussions upfront before the Contractor goes off and does the quotation.