I dont think the 35f1.4 Nokton is expensive - however I think a used Summilux 35f1.4 pre-asph at $1000 is overpriced!
The cost of developing a lens and manufacturing it it is related to the complexity of the design. Just adding 1 more element changes the whole design criteria. The 40f1.4 was designed to be a good performing, semi-normal focal length and the "look" was designed to give a modern look to its image (though we have the choice of MC and SC to).
The 35f1.4 Nokton was designed to give a more "vintage" look to its rendition, more like a Summilux 35. In so doing CV also corrected for some of the obvious weak spots of the Summilx 35 - flare sensitivity, coma and some of the spherical aberations, but without touching the "look". The 35f1.4 pre-asph had an almost "cult" like following in Japan with prices reaching fantasy levels and the Nokton 35f1.4 allowed users to get a better, but similar lens at an affordable price.
Product pricing is not always the fault of the manufacturer either. Dealer and distributors play a large role here. A popular lens that flies of the shelves can take a bit of a price hike - and to some extent "subsidize" the less popular lenses.
All the major distributors pay virtually the same for a given product - it is then up to them to price it and if they feel that lens A can handle a higher price, they will put it higher and if lens B is slow mover, they can drop the price to make it attractive.
And talking about expensive. I just used the Summilux 21mm f1.4 Asph - list is about $6000!!!! It is a incredible piece of optics - and it is the only one of its kind - hence the price can be what the market will handle. If, at some time in the future, another manufacturer comes out with a similar lens - the price would have to be adjusted. Is it worth $6000 - I dont know, but if I had $6000 I would buy it! Now a 2.8 works fine too - and you can get a Zeiss 21f2.8 for $1100. Just like with super-cars - it is those last 40-50mph or 0.1 of a sec off 0-60 thats costs money.