This is not a fair comparison. Due to selling format : auction, buy now, timing ,etc. A big factor in ROI is TAT . So the variables for everyone is different.
These are all Gem mint or Pristine , same card same time frame (last 2 weeks).
card #1
Raw $15-20
PSA $50-85
SGC $35-45
CGC $30-40
Card #2
Raw $5-7
PSA $23-35
SGC $21-29
CGC $17-25