The Used RTX 3090 in 2026: Why a Five-Year-Old GPU Is Still Local AI's Best Deal

24 GB of VRAM and 936 GB/s for around $700 used — no current card touches that math. Real owner reports on why the 3090 remains r/LocalLLaMA's default answer, the dual-3090 70B rig, and how not to get burned buying one.