Welcome back Harrie. It's been a while.
You're looking for the impossible. Age and mileage of ST1300s is exactly what determines their price. Cheap recent ones don't exist. You want cheap you take older high mileage bikes. If you browse the web you'll find the bikes built since 2010 command more than $10,000. So if your wallet holds $5000 you're not going to get one except from someone who is desperate for a sale or who knows their bike has a $5000 fault. Realistically, for that money you'll be looking at a 2005 bike with more than 50,000 kays experience, and which still has at least 100,000 kays before it might give any trouble. You might find exceptions, and they might have been dropped.
How long is a piece of string? So many ways of looking at this, so many answers, non are correct, all are correct.

Just had a quick look at BikeSales, quite a few available, quite a range of (asking) prices, and as Mr B suggests the relationship between $ and km sets a pattern, but there are some exceptions. eg.
* The lowest km ST (3,649) is priced at $5,000 below an ST with approx. more 10,000km. I doubt whether there is much difference in the condition of both, but at $5K less, I'd certainly prefer the lower km's.
* There's a few ST's in the $8,200 to $8,500 range, the one above with 3,649km another with 63,000km. Again, I'd certainly prefer the lower km's.

I haven't looked at any of the ads in any detail, some of the description may explain the disparities, but on the surface the ST1300 with 3,649km at $8,500 looks worth a look or three.
Disclaimer: I'm not associated in anyway with the seller of that ST1300, or at least that I know of .....
Finally, my ST1300 just ticked 30,000km on the way home from the last ride, it's not on the market, but if someone is willing to offer me $20,000, I would consider it (in other words, I don't want to sell).