Why is the price of new tonearms so high

Which tonearms are you talking about? The Graham Phantom II B-44 Tonearm is $4700. The SME Series V is $5300.

Or am I mucking about in mediocrity here?

Those are very nice arms but Im thinking of Venomous prices like twelve Grand and more.

There are various reasons
Marketing
the higher the price the more people think "it has to be good"
Mark up
The higher it is, the more dealers are interested to get it
Quantity
Analog sales are not comparable to those 10 years ago
Quality
Today we have much better machines, more precise and cheaper in production *aehm* did I miss something?

I know most arms, or listened to them, most are not worth their high price (from performance in comparison to other but I am afraid, no one is interested in that).
Analog is on the way to become a "Boutique Product", it's nice to have, the next step of "My Horse-My House-My Boat and it is better to sell 5 units for a very high price than 30 for lower price, less work, less discussions and for final one can say:"Well, you know, it is NOT for everyone"

Price has -unfortunately- not a direct link to Performance.
Marketing has own rules :-)

Buconero and Syntax I agree with you, manufacture dont seem to be high. And the Physics shouldnt have evolved as much as electronics so old sound concepts should still aply. I just dont understand why nobody starts to manufacture the old(not all of them but the good ones) arms again?

One reason is because if someone has a $5000 tone arm and wants to upgrade he/she would need to have something to upgrade to. Thus the $12,000 tone arm. It is seven thousand better. The true problem arises however when someone with a $12,000-$15,000 tonearm gets bit by the upgrade bug. They soon realize that there is nowhere to go, they have hit the end of the upgrade highway and give up on audio. Or, they get a Mac and a DAC and take up golf.