You need to leave much more room for context if you want to do useful work besides entertainment. Luckily there are _several_ PCIe slots on a motherboard. New Nvidia cards at retail(or above) are not the only choice for building a cluster; I threw a pile of Intel Battlemage cards on it and got away with ~30% of the nvidia cost for same capacity (setup was _not_ easy in early 2025 though).

You can gain a lot of performance by using optimal quantization techniques for your setup(ix, awq etc), different llamacpp builds do different between each other and very different compared to something like vLLM