Hi Martin,
Massoth XLS, item 8220530 is the one pre-programmed for the V60/V260 I believe (though most stockists both here and in Germany will programme a generic stock one with whatever sound file you need). About £160-£180-ish, including speaker, over here (shop around for best price, they do vary!) - or about £147 direct from Germany, but watch out for flat-rate shipping charges. Very straightforward to fit, all connections to the decoder are via screw terminals so you don't need to do any soldering. Someone recently posted a similar installation on here for a Piko BR199/Harzkamel, showing what to do with the power and lighting connections - your V260 will be pretty much the same. The only (slight) complication is making sure you remember to adjust the relevant CVs for the lighting voltage before applying track power, as the lights are all LEDs.
There are other sound decoder options, such as the ESU Loksound, which some folks on here like a lot - I only suggest the Massoth because that's the one I'm most familiar with myself. The Piko option, as you've noticed, seems extremely expensive for what it is - possibly because it's two separate units rather than a single integrated driving and sound decoder. I think the Piko units are actually re-badged Uhlenbrock decoders and Dietz (or is it Zimo?) sound units - others here know more of this than I do and can confirm or correct.
Jon.