The emerging integration of Terrestrial Network (TN) and Non-Terrestrial Network (NTN) Base Stations (BSs) is anticipated in 6G to cope with the ever-increasing capacity demands, with the optimal decision on which to deploy and where to be one of the main problems. In this paper, we focus on minimizing the Total Cost of Ownership (TCO) of the different terrestrial, aerial and space BS types while satisfying the 6G traffic requirements. Although related work focuses on the improvement of resource allocation and network automation, the financial aspects of the new access nodes and their effectiveness remain a lesser topic, which is thorough analyzed in this study. In particular, a detailed energy and cost analysis model is proposed for the 6G access network, which is expected to be the main energy bottleneck, employing different BS types and analyzing their main differences. Then, the total TCO is evaluated for each BS type under different use case scenarios. The provided results demonstrate that NTNs can achieve up to 4.4 times lower TCO in coverage driven scenarios, proving that an integrated TN-NTN architecture is of vital importance for 6G.