If you are not an Indian passport holder, and you buy the combined ticket of EUR 12.5 for Taj Mahal and Agra Fort, two UNESCO World Heritage Sites, it works out to EUR 6 or so per attraction.
Here's a comparison with other sites, from a mix of developing as well as developed economies:
- Tickets to Machu Pichu in Peru are EUR 18.
- Tickets to Angkor Wat in Cambodia are EUR 10.
- The entrance ticket to the Colosseum in Rome is EUR 16 for non-EU nationals, and there is a discounted price offered to EU Nationals of EUR 11.
- Tickets to the Leaning Tower of Pisa are also EUR 16 at the moment
- Tickets to the Giza Plateau and at least one pyramid - say Khufu - cost EUR 18.
- Entrances to the Forbidden City in China are only EUR 4 (but that may be because the exchange rate is artificially held by the Chinese goverment).
As far as the differential pricing for Indians is concerned - The Government of India subsidises tickets for Indians to promote our heritage and create more interest / awareness / national pride. Additionally, in a poor country, there is no way the man on the street can afford the kind of the prices that these monuments deserve. This is a dent in the Government coffers, but it is a decision in the national interest which the Tourism department has the right to make.
There is obviously a case to be made for levying flat fees for everyone - Indian or foreign - and I've heard that they're considering flat fees of INR 250 or so. But honestly, if you've been to Taj and seen the number of poor people that come there - none of them could afford this.
In any case, until we hear any decisions, all that I think you should ask yourself as a tourist is - am I paying a fair price i.e. did I get my money's worth at these two monuments for EUR 6 per monument?
I think the answer is likely to be a yes.