How do I motivate pursuing a PhD in Computer Science (CS) after a BSc in CS and MBA in Finance
You're an excellent candidate for a PhD in Computer Science: You have a BSc in the subject, you have six years of industry experience, and you've developed a strong urge to pursue CS again to deepen [your] understanding of specific fields of interest while contributing in high-tech and R&amp;D industry. (A desire to deepen your knowledge isn't enough, you need to be truly passionate about contributing in high-tech and R&amp;D industry. I presume you are.) Your MBA gives you business know-how that'll focus your attention towards research problems that'll have real impact on society.

From the research I've conducted most entry requirements prefer applicants to master computer science as it's most ideal but a 2nd master's degree (in CS) is rather deterrent from a time and financial perspective.

Entry requirements are tailored towards the average entrant, which, I'll speculate, is someone that's never left university. You aren't an average applicant. You can confirm my theory by calling some admission departments. Thereafter, identify supervisors that pursue research that impacts technology. Pitch yourself to them, explain how your skill set will advance them. Establish whether they can help you on your pursuit.