The increase number of mobile users in wireless environment affects query access time substantially. To minimise the query access time, one possible way is to employ data broadcasting strategy. In this paper, we propose cost models for both query access time over broadcast channel and on-demand channel. We examine the cost models to find optimum number of broadcast items in a channel while utilising query access time over on-demand channel as a threshold point. The optimum number indicates a point to split the broadcast cycle and allocate the data items in the new channel or else the on-demand channel outperforms the broadcast channel. The cost model involves several factors that dynamically change the optimum number of broadcast items like request arrival rate, service rate, size of data item, size of request, and bandwidth. Simulation model is developed to verify the performance of the cost model. This paper focuses on request that returns a single data item.