Should I spend money on DDR3 RAM for an old OptiPlex 7010?

Probably not worth it. Even if you find 2x8GB sticks for $20 on eBay, that $20 is better put toward a used Dell with DDR4 and a much faster CPU. The 7010 will still feel slow in 2025 due to the processor and old SATA storage—8GB to 16GB helps if you’re hitting swap but won’t fix the bigger bottlenecks. Save your cash for something that won’t feel like a time capsule.