I looked this up (saddo) and she was estimated to be worth about £3.5 million pre-marriage. There was an Elle article from the start of July (so pre-Dublin trip and the polo the other day) which said her wardrobe to date was valued at £750,000- not including bags, jewellery and other accessories, and it's been paid for by the Duchy. If it wasn't she'd be nuts to be spending 20% of her net worth on bloody frocks!
I know she's now royalty and has to maintain a "look" but really, it's all a bit much. You expect big money on outfits for major events (weddings, state dinners, etc) but she could pare it back on occasion. We're not expecting her to rock up to stuff most of the time in New Look gear, but more higher-end high street brands would be a good idea.
You just have to look at the Yorks as a bit of a cautionary tale- people only love the glamour for so long, but as the novelty wears off and you get shoved to the sidelines to make room for the immediate heirs (George, Charlotte, Louis) people will be much less forgiving of seemingly lavish expenditure, even if it's paid for out of private funds.