Rich doesn't equal stupid. Quality is very often worth the extra money. A truly unique, hand-crafted, item is far superior to any mass-market product of the same quality. People pay that much for "frivolous" things not because they are stupid, but because they recognize that workmanship is worth a premium price. Time is money, as they say. Even if it only takes a turner 30 minutes to produce a fine quality pen that's what, 1 100,000th of the production of a mass-market pen producer? 100,000 to 1 odds produce a huge supply and demand premium.
As for $150-300 being a good day's pay, some folks wouldn't consider that even close to a good day's pay. Some wouldn't even consider that a good hour's pay. It's all relative.
I suspect that after turning 5 days a week for 52 weeks you'd find it far less enjoyable than it is now as a hobby. That also assumes someone else is doing your marketing and shipping, your accounting, and all the other aspects involved with doing a business. If it does, now your $150-300 a day in earnings can be cut by at least a third-more likely 1/2, and that doesn't even cover your actual consumables expenses. Factor in the cost of your wood, your electricity, your maintenance and you're at best down to $30-120 a day pre-tax. Is that enough? (~$11k-$35k) Is that a good living well above poverty level?
Now take out taxes... how's it feel to be "doing what you love"?
It's not that simple, when you start breaking it down. The value on those pens is worth it, when comparing apples to apples. Does it make people stupid for paying that price? Obviously that's subjective, but I'd argue not. It just makes them people with either more disposable income or a true respect for the value of custom workmanship.