In the Mad Hatter's tea party, featured in "Alice in Wonderland," what was the price marked on the hat?

I often have to look up equivalent currency conversions. In Dickens, Scrooge's assistant:" how much does he earn a week?" or an urchin in Oliver Twist:"how much is half a crown, that he thinks he's rich?"

The weirdness of the names given to Brit money fits right in their weirdness.