Best cheap pads for upstairs treadmill vibration. What actually worked for you?

Here’s what helped me most so far:

• Foam tiles under a flat shelf board
• One anti-vibration pad under each foot
• Leveled and re-checked after 20 minutes at 3 mph

Regular treadmill mat did almost nothing.

Foam tiles + flat board + basic washer pads (whirlpool from lowes) helped impact noise, less so vibration at ~3 mph. Has anyone compared Whirlpool pads to Sorbothane hemispheres or a stall mat platform? What actually reduced vibration into the floor for you?

materials cost was about $20 to DIY but just wondering if that was worth it vs just buying a higher end pad. Happy to share how i did my setup too if anyone curious