Apparently the price you are quoted when you search for fares on Spain’s high-speed railway depends on whether you search in English or Spanish:

When I searched the site earlier that day from my office, I searched in Spanish. A one-way ticket from Barcelona to Madrid could be had for around 44 euros on a “tarifa Web,” their Internet special fare with 30 day advance purchase.

When I was at home, ready to finalize my purchase, I opted to search with the site language set to English. The price was nearly 110 euros.

The economic logic is standard:  language is a way to segment the market and this segmentation is profitable if the two markets have a large difference in price-sensitivity.  Presumably if you are searching in English then you are a tourist and you have fewer alternative modes of transportation.  This makes you less price-sensitive.

I thank the well-travelled and multi-lingual Mallesh Pai for the pointer.