Every card detail page has a Price history chart. By default it shows the raw market line; click any grade in the price table to overlay a line for that grade.
Line colours match the company palette: PSA is gold, BGS is blue, CGC is violet, TAG is emerald. Individual eBay sold transactions appear as small dots so you can see the actual data underneath the smoothed line.
Time range selector (top-right): 7d / 30d / 90d / 1y / All. The default 90d window captures most short-term moves without being too noisy.