This article does a great job of describing the minimum level of quality allowable to scrape past certain stages of growth.
The question you should be asking is: what level of quality, built in from the beginning, intentionally and with full support, will create a product so valuable to the customer as to generate a wild feedback loop of success—not just scraping by at a minimum acceptable level. What level of quality will generate returns, not just reduce your debt to an acceptable level? And more importantly, how do you achieve it?
Quality is your value to the customer. If you think of it systemically, you won't need a QA. As Dr. Deming said, "Inspection does not improve the quality, nor guarantee quality. Inspection is too late. The quality, good or bad, is already in the product." And Harold F. Dodge: "You can not inspect quality into a product." Deming advocated instead for a holistic understanding of the factors driving quality, including management and leadership, the processes used, and continuous improvement of systems.
This is the type of discussion I always see lacking from discussions of software QA. On the manufacturing timeline, it's like we're in the 1920's. It's all very realistic, but we could be so much further along.