How can I lower the cost of this gaming PC build without losing much performance?

This is already close to the lowest-cost version of the build. Look for the best current deal on the RX 9070 XT, use less expensive 32GB DDR5-6000 memory, and compare SSD and case prices. If you have wired Ethernet, choosing a motherboard without built-in Wi-Fi can save a little more. The graphics card is the part worth downgrading first if you still can’t meet the budget.

The Ryzen 5 9600X is perfectly capable for high-refresh gaming, including 100-plus FPS in many games, so you don’t need to replace it with a 7800X3D unless you’re specifically targeting very CPU-heavy titles. A cheaper motherboard and a normal DDR5-6000 CL30 kit should reduce the total without noticeably affecting performance.

The biggest savings should come from the memory and graphics card. DDR5-6000 CL30 is already excellent for this platform, so there’s little practical benefit to paying a premium for a CL28 kit. Also compare several RX 9070 XT models because prices vary a lot between retailers. If the XT still pushes the total too high, a standard RX 9070 is the easiest performance-preserving downgrade.