"Really the only way you know for sure is go through each national rail site, get the price of the ticket and add it up"
If you just get the price of a full fare ticket they might add up to more than the cost of the rail pass, but that would be wrong. There are a lot of ways to save vs full fare tickets.
For instance, there is a EuroCity train (EC) every two hours from Berlin to Prague. Full fare is 67,60€, but you can get an advance purchase SparPreis (Savings Fare) ticket from the Bahn website for 29€.
Or, Salzburg to Munich would be 32€ to 36€ per person on an EC or RJ (RailJet), but with advance purchase, you could get a ticket for 19€/P. Or, for regional trains, you can purchase a Meridian Guten Tag Ticket right up to train time for only 21€ for the first person.
Every Land (state) in Germany has a regional pass (Länder-Ticket) which allows unlimited travel on regional trains all day for a low price (23€ in Bavaria), and the Bahn has the Quer-durchs-Land-Ticket for weekdays or the Schönes-Wochenende-Ticket for weekends for unlimited travel all across Germany for a day.
Just don't use full fare tickets in your comparison with a rail pass.
Also remember that in most countries, the faster trains require a supplement (called a reservation) to ride them with a rail pass. Be sure add reservations to the cost of a rail pass.