The Palace of Westminster took 30 years to fully complete and that was publicly funded. Sagrada Familia was built - insofar as it hase been to date - by personal finance and donations, and ticket sales.
In today�s terms (broadly) the Palace of W's build budget was �51m and it actually cost �160m. A bit like most of our public capital projects today I suppose.
Gaudi left many architectural treasures in Barcelona, I would urge anyone to go and see for themselves.