Hi Rune
The Roundhouse Argyll was produced from 1993 until 2004 and was advertised by a dealer in 2004 at £1270 for a radio controlled version.
I have a late one and it is a superb loco - it is very controllable as I quickly substituted 2.4ghz radio control. This is just a matter of changing the transmitter and receiver - but you will need to budget for this unless it is manual.
It is very different from the Atlantic as has been said. The Atlantic has the correct, rivet free smokebox and is fully sprung. The Argyll has the great advantage (in my eyes) of the spoked wheels.
Simon Whenmouth of Anything Narrow Gauge has an Atlantic for sale at £1050 and a fully lined Argyll at £1150 (these are on his page on my website). His locos come fully checked and guaranteed though. You will see that the new price ten years ago has no relevance now - it depends on specification, colour and condition.
Ideally you should see it in steam as it may require a little fettling after ten years in a box. Some of my locos play up after aafter just a few months on the shelf, but the great thing is that Roudhouse locos are easily sorted.
If you can get at the screws under the smokebox, it is easy to fit a Chuffer to an Argyll. If not, it is a boiler off job, but not difficult.
Good luck!
Cheers
Chris
www.summerlands-chuffer.co.uk