In my view while it's true that the prices for Dutch style bikes seem high, they come with everything. Finding after-parts that actually fit a regular bike could end up costing even more. I know this because I've assembled a bike that's close enough, by accumulating cast-off parts over the years, but when I look at modern bikes and add up the cost to build the same from new parts, it really adds up.
I personally find the bolt-upright posture to be uncomfortable, especially on hills, but it's not obligatory on those bikes. Most are reasonably adjustable.
Germane to the comment about buying a 40 year old bike, city bikes with fenders and chainguards were common in the US at one time, albeit with different aesthetics, and one could be refurbished to function quite well for the intended use.