The HYLIFE-II concept uses the molten salt, Flibe as the primary coolant for the liquid jet flows in the reactor and uses sodium fluoroborate (NaBF4) in the secondary loop. The impact of these molten salts on the direct capital cost of the balance of plant (BOP) and on the cost of electricity (COE) has been investigated. The RUBY computer code has been written specifically for these molten salts and includes detailed analytical models for the intermediate heat exchangers (IHX's) and the steam generator system consisting of separate evaporators and superheaters. Using the RUBY code, the design of these large and costly heat exchangers and the associated tritium removal system has been optimized to yield the minimum COE. The cost models used in the code are described and the results of the optimization are given.