This contains the first published account of "A penny for your thoughts", possible root origin of "my two cents worth".
If we take the 1546 publication date of Heywood's tome as the date of origination, how do we determine inflationary value today? What goods and services might be comparable?
In 1521, Heywood received a 10 mark annuity as the king's servant. There are 240 pennies to a mark, so that was a yearly salary of 2,400 pennies.
According to online job search sites, butlers in London can expect salaries from 22k to 42k (pounds sterling). That means 2400 pennies might equal 42,000 pounds today, or 17.2 pounds per penny.
Today's conversion rate is 1.73347 dollars per GBP. That means "My Two Cents" would be worth about $59.63, or possibly more depending on how far back past the 1500s the phrase originates.
As an interesting aside, if you deposited a penny in a London bank in 1546 at 2% interest, in 2008 your account would hold 94.03 pounds, or 162.99 US Dollars.