cannot dollar-quote $$?$$ in PreparedStatements

With 8.0 postgresql and driver, this works fine:
ps = con.prepareStatement("insert into product values(?, '?' , ?)");

But this fails:
ps = con.prepareStatement("insert into product values(?, $$?$$ , ?)");

It looks like "someone" (driver or engine?) is counting 3 parameters instead of 3:

org.postgresql.util.PSQLException: Pas de valeur specifiee pour le parametre 3.
    at org.postgresql.core.v3.SimpleParameterList.checkAllParametersSet(SimpleParameterList.java:102)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:166)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:389)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:330)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeUpdate(AbstractJdbc2Statement.java:282)
    at TestFetchSize.main(TestFetchSize.java:86)


How dollar-quoting and question marks are supposed to interact?
Sorry if this a well-known issue.