During power deregulation, member companies are releasing their transmission grids to form ISOs/RTOs/Mega-RTOs and they cooperate to run the united system while to achieve their own economic goals. Since there are multiple existing state estimators distributed with different owners in one ISO/RTO/Mega-RTO, these neighboring estimators in single power market can exchange their data, where the term 'data' refers to both raw instrumentation data and estimation results of other estimators. It has been demonstrated in our previous publications that carefully selected data exchange schemes improve the quality of estimators in individual entities on both estimation reliability and accuracy. In addition, data exchange is critical for the newly proposed textured distributed state estimation algorithm over the whole Mega-RTO grid. Since all the activities in a market environment need to be evaluated in terms of 'price', the following questions then arise: how to price data exchange activities in a power market? And how to search for the most valuable data exchange schemes in term of market price? In this paper a pricing methodology for data exchange is proposed based on the concept of marginal price. Furthermore, a systematic approach to search for the most valuable data exchange schemes is proposed based on some heuristic rules. Numerical tests verify that the proposed data exchange pricing method is valid and data exchange activities have major impacts on traditional measurement placement design.