I got my F50 s/h for a profit some years ago - it came with a 'job lot' and I made more selling the bits I didn't want than I paid for the job lot

You can have mine for £50 (the little plastic bit that is)

I bought mine for about £250 new a few years ago. I suspect these are a small number of unsold stock from the back of a warehouse somewhere, as it is not on the Pentax roadmap. I doubt it is production any more.

At that price it is my second most valuable lens now (after the 60-250 - for which I also paid rather less than the current price)

I rate it highly myself and it gets a lot of use. Of course it is not as sharp or fast as my 60-250 - but that is hardly a walkaround travel lens! I think it performs pretty much as well as the 18-55 within the same range. I don't have the 55-300 so I cannot compare (and that too is f6.3 at the long end) but it is no worse than my Sigma apo macro DG 70-300 at the long end.

That will be it... Much easier to design a sharp prime - especially at a relatively straightforward focal length such as 50 mm - than a zoom. Compare modern zooms to 30 year old zooms and there is no comparison. Some of the Pentax MF 28-70s and 35-70s of yesteryear are seriously mediocre.

It won't be necessary either - it comes with its own drop-in 40.5mm polariser.

I suspect that the price is less likely to 'even out' if there is no 'competition' from the Tamron badged version (as there was with the 18-250) - though having said that the Pentax 10-17 was considerably cheaper than the Tokina version for other mounts (The Tokina actually came out later than the Pentax in this case)

The press release says clearly it an SDM and not a DC lens - but I am not sure I entirely believe they will be taking out the Tamron motor and putting in a Pentax one, despite the implications of the press release.

Residual value is relevant - partly why I bought the Pentax badged 18-250 a few years back - but I am not sure it really justifies the price rise!

The new 18-270 looks suspiciously like a re-badged Tamron.

I've nothing against that as I have the rather serviceable 18-250 which is also a Tamron rebadge (right down to hood interchangeability - I lost my original hood and so replaced it with a Tamron one as it was less than half the price).

However the 'RRP' of £699 is currently nearly double the street price of the Tamron equivalent. Now RRP is one thing - but even if the street price is - say - £500 Pentax are still taking a £140 premium for taking the IS out of the lens (and - if the blurb is to believed, putting in their own SDM motor in place of the Tamron PZD one).

With the 18-250 you could choose which to buy as the Tamron version was available in Pentax mount (I bought the Pentax at a premium of about £50). With this model you do not have that choice and the there is no 'native' version in Pentax mount.

And while on the subject of lenses - I wonder if the 560 5.6 is actually a lense (and therefore does not really exist...)

No, walkeja is correct here. Walkeja is, I believe, expressing the fact the the word 'ltertes' is missing from his original post.