difference in train ticket prices between different sites

Non-local rail websites only show reference fares, not the real local deals, specials etc. That's why even though DB's website might be more comfortable to search for timetables the binding fare is the one you find on the respective country's rail website.

Where have you found fares between Spanish cities on the Bahn site? Usually DB only gives fares for connections between Germany cities or from a German city direct to a city outside Germany.

Occasionally, they will give a fare from a German city to a city outside Germany that includes a leg completely outside Germany, but that is in conjunction with a multi-train connection from a German city. For instance they might give a fare from Basel Bad Bf (in Germany) to Interlaken that includes a separate train from Basel SBB (Switzerland) to Interlaken Ost, but if you just put in Basel SBB to Interlaken Ost, it will say "Tariff abroad".

So, yes, you should use Renfr.es for tickets entirely inside Spain.

Most country's rail company don't even give fare to cities outside the country. (Try to get the fare for a direct train from Vienna to Prague from either Austrian or Czech Rail.)

Are you sure you are not looking at RailEurope? They will give international fares, but at high prices because they are resellers.

And you can check prices and book tickets in English on the RENFE website. Switch to English down the left side where it says "Seleccione su idioma"

it might have been the Raileurope site, but I reached through the link to Deutschebahn on this site.

thanks Norm. I got the link to renfe.es from a Spanish speaking resident of Madrid who told me it wasn't available in English so I didn't look for myself.

Sherry....I think it's a plot to make us think Spanish is taking over the world. ;)