They are a complete waste of money. With my first child I did the usual 'Oh has to be the best of everything' and went for the ubiquitous Cath Kidston £65 changing bag. It's marvellous how well their marketing appeals to us. As if a wipeclean, somewhat actually heavyweight bag to weigh down your pram with it's many compartments and gosh a 'handy' key fob actually does any different a job to two Tesco carrier bags that weigh nothing with nappies in one and bits and bobs in the other.
Seriously, there are some that actually state boldly 'Yummy Mummy' as the brand name. Let's be clear, a yummy mummy is just another expression for MILF, which in my opinion, being as it was first bandied about in lad's mags, is not complimentary.
Your argument will be, ' but the compartments are so handy for storing the bottle upright, it's easier to find my keys than delve about in the pram basket or handbag, I can fit a change of clothes in there too'.
You can do all that with carrier bags and a bottle holder ... but it's not quite the same pulling out a supermarket carrier bag full of changing gear in the middle of the playgroup, you must have a branded changing bag with florals and 'statements' to be in the proper club. They range from £60-£185. It's a flippant design choice, not a practical choice...
However, new mums are the biggest known captive audience in the commercial world, nothing I say will change a single person's mind! 