I have been to
Israel many times. One thing I learned there is never give up. If they tell you you have no
hope of getting your coins back - don't listen to them. Keep
writing and calling and harassing them. Demand a legal explanation. Write an MK or two and tell the custom's officials what you have done. Tell them you need all the facts from them to support your lawsuit against them. Etc., etc.
Either this is the beginning of a new and serious crackdown or you have been unfairly treated by an arbitrary official as others said.
Joe is right that strangely coins are more expensive in
Israel. I have got ok deals on some uncleaned lots there in the past, but only in person and only when I literally spend an entire day getting to know the vendors - visiting their
home, etc. The prices of individual coins tends to range from slightly above
average to outrageously high.
What works in your favour here is that some Israeli dealers (I know for a fact) import some of the coins which they then in turn sell. This means that such a ban will hit them too.
SC