dances agree, was just about to post to say to the OP, what if one of your children happens to be very gifted at dance, singing, choreography etc.? Do you want there to be nothing for them to aspire to?
So called "elite" arts have more effect on our economy than just the tickets - my brother for example is an architect who specialised (until recent funding cuts) in building and renovating theatre, opera and gallery spaces - his whole practice benefits from lottery arts funding for theatres, opera houses and galleries in cities throughout the UK (take a look at how many cities have big and small theatres and opera houses - the result will surprise you). His practice wins funding bids, employs builders, secretaries, contractors, all generating jobs and income...
The net economic and social benefit of the arts is very high across the country. The ROH functions as the flagship which helps maintain the rest. For example, it also acts as the home to our best ballet and opera companies - dancers and singers come from around the world to be there. British ballet training at the various Royal Ballet schools and companies is renowned as one of the best in the world - in the best three or four ballet traditions in the world (easily up there with the best Russian schools, the New York City Ballet and so on). It's simply not true to say ballet and opera just have their roots elsewhere - there is a long tradition of British ballet training and choreography dating back to the late nineteenth century, for example. The ROH supports it's companies and the Royal Ballet School; they also support sister and other companies throughout the UK such as the Birmingham Royal Ballet, providing training and jobs for dancers, keeping the art going, keeping innovative choreographers going....
Set against your 26 million, take a moment to consider that more than £4bn a year, nearly £5bn, of public taxpayers' money, goes every year in capital grants and subsidies to privatised transport companies like Stagecoach, Railtrack etc. for them to cream off in profit to shareholders, and apply your own argument. Which would you rather pa your taxes for, 26 million to support art, maintain a historic building, support whole artistic industries and do education and outreach work at the ROH, or pay it to Railtrack's shareholders?