Security Information and Event Management (SIEM) systems are crucial for modern organizations, gathering and analyzing events from various systems to detect and manage security threats. The blog explores the trade-offs between building a custom SIEM using free and open-source software (FOSS) versus adopting commercial solutions, highlighting that while FOSS may appear cost-effective, it involves significant operational costs and maintenance efforts. The evolution of SIEMs, driven by advances in cloud technology and AI, has made commercial solutions more affordable, often adopting flexible pay-as-you-go models. These solutions can alleviate infrastructure maintenance burdens, offering significant cost management benefits. However, choosing between a DIY or managed SIEM solution requires careful consideration of both capital (CAPEX) and operational expenditures (OPEX), as well as the technical capabilities necessary to meet an organization's security and compliance needs. Ultimately, organizations must weigh the hidden costs and operational demands of FOSS against the benefits of cloud-based SIEM solutions, which offer scalability and ease of use, to determine the best fit for their security strategy.