Scrabble tile values were set in the 1930s by counting letters on a newspaper page.
A study of all 172,835 words in the ENABLE list found that tile values are accurate at extremes (E cheap, Q/Z expensive) but have 11 inversions where a higher-value tile is actually more common.
Example: H is worth 4 points but appears more often than B (worth 3 points).
The longest isograms (no repeated letters) are 'dermatoglyphics' and 'uncopyrightable' at 15 letters.