Although 50% of the price of a ticket goes directly into the prize fund, so it's not purely a tax increase is it.
And as said 27% goes to charity, so that not really a tax increase either. More a good will increase.
Then there's running costs. I'm sure Camelots running costs have gone up in the last 19 years, the same as any other business.
It's quite a complex thing, and no doubt the government will recieve more tax from the price rise, but it's not a shocking move in my book.