A company by the name of Grey House Publishing markets are variety of
useful industry guides and also publishes the following book, which is
available at a great many public libraries:
"The Value of a Dollar: Prices & Incomes in the United States, 1860-1999'
Grey House Publishing, Millerton, NY 12546
Our first instinct in seeking prices might be to go to the microfilms
of old Sunday newspapers because few newspapers are indexed before
1980 online. But you'd be fishing -- and the book "The Value of a
Dollar" has already pulled out many, many popular items from
newspapers, catalogs, and magazine advertisements. For the 1960s
there are 49 pages; for the 1970s another 38 pages with pricing of
staples (beef, milk, eggs, coffee, bread, etc.), homes, cars, and
consumer items. It's cleverly edited, so the real danger is that
you'll get distracted by an article on the "new" high in baseball
salaries. But it will also give you wonderful ideas about things that
you could add to your baskets to make it even more fun.
I didn't see the price of a Snickers candy bar, but did find the
following 3 prices from 1965's Western Auto catalog:
Mattel Teenage Barbie: $2.29
Mattel Midge Bride (Barbie's girl friend): $2.69
Matel Ken: $2.69
You find many common consumer goods, such as the price of a 6-pack of
Pepsi from the Chicago Tribune.
A couple of additional notes for you:
* if you're seeking the price of a long-lived brand, like the
Snicker's Bar, I'd send a query through to the PR staff at the
company. M&M Mars breaks down all of its products by brands (and
country) at http://www.mars.com
* the New York Times is available back to 1851 online via a service
called Proquest Historical Newspapers. The reason that I mention it
is that it's fully indexed -- and though Proquest is a fee-based
service, many public libraries have the Internet access for free.
Mine does and it can be used from home as well. A search for Snickers
in the date range of 1960-1970 might give you very precise
information, such as when the company changed its retail prices (or
Google search strategy:
"Value of a Dollar"
"Value of a Dollar" Grey House