Urm, do you know the meaning of kosher ? Is there any meat in your package and remember you are willing to send to Germany... I would be very careful using such an allegation.
In the UK, almost no courier will insure a musical instrument for more than £100 GBP, EuroSender does up to 2000 Euros (it's a logistics company now based in Luxembourg, hence the Euros) and I've been using them a lot for instruments up to that value.
Otherwise use UPS or Fedex and pay the full expensive fee, but read carefully the small print...
A last recommendation : if you are the seller, always arrange yourself the shipping fully insured and trackable. Also remember that, by eBay, the buyer has to pay for the whole shipping fee including insurance and tracking number. Don't do so, then the eBay cover is void: it's as simple as that.