Chia has posted plotting times on different machines as reported by some early testers.
Here is a few of the results, just listed by the ones that seem to be most important to me.
Example:
Processor i9-10850K – 2 SSD drives – 64GB ram – 4.7 hours
Processor i5-2400 4-Thread – HDD drive – 8GB ram – 21 Hours
The biggest difference is that the plotting with SSD is about 4 times faster than plotting with hdd. The reason is simply the write speed to a SSD is faster than writing to a hdd.
Here is the whole reference list on Chia.