As has been said, pay what you want if it makes you happy. In my mind, the prices of clubs have gone silly recently. The latest Callaway irons are getting on for double what I paid for them 3-4 years ago. My XR16 driver cost me £200 (ok in a pro shop sale). Modern drivers are again getting on for double that. Where is the justification?
And whilst you can't buy a good branded driver new for less than £300 now, there are other, lesser brands that perform well for your normal average club golfer. And for putters, it's more to do with the person on the other end than the club itself. You get a club you feel comfortable with and then work with that. But paying £300 for a club won't make you a better putter or drive the ball straighter or longer (yes, there have been improvements in distance but not much as much as the manufacturers would like you to believe).
But then again, I'm a tight a*** and don't see the need to pay that much money.
Ah, what the hell. If you like it and can afford it, go for it. You use the putter more often than you use your driver so why shouldn't it be as horrendously overpriced as the driver?