Software testing outsourcing appears to be the best alternative to acquire better software quality with competent ratification by extrinsic parties who have the capability to do it. Through the effort, organizations are peeking to promising benefits constitute in it such as current testing technology, experts, an abridgment of the project's duration and more concentration on the main organisation's activity. Along with these benefits, one important reason that encourages the decision is optimization of cost expenditure, which the strategy is perceived as a good move for a competitive organization. However, implementing such preference eventually results in a different outcome. Organizations have to bear the higher cost and incur losses of cost deviation from the expected estimation. The conflicting between cost and benefits raises an important concern of striving better cost estimation for such projects. This paper aims to address this interest by analyzing the existing literature in order to identify the contributing factors towards better cost estimation for software testing outsourcing project-context. The analysis is done using the content analysis method. The results could be divided into two categories; which are the cost items and contributing factors. Cost items consist of direct cost and indirect cost, which refers to the expenses for the project. While the contributing factors consist of people and environment, which are needed to produce accurate cost estimation. The findings provide an insight to excogitate attentively the essentials in the endeavor of improving the exactitude of cost estimation for software testing outsourcing project.