RFID (radio frequency identification) is a rapid-developing technology for wireless identification lately. How to speed up the processing procedure of RFID data is a critical issue needing to be addressed in terms of a real-time RFID application. In order to work out the processing speed problem, data grids would be a promising solution to the huge amount of RFID realtime data due to the high performance computing capability and distributed storage system. However, there are still differences between RFID system and data grids such as protocols, programming interface, and security issues. Therefore, we suggest an intermediate architecture called RFID-grid proxy between RFID networks and data grids system with a view to interconnecting two different systems. In this architecture, we have evaluated a probabilistic cost estimation model of M/M/m queuing system for RFID jobs considering the system load balance, real-time throughput, and deployment cost.