[devote]

var re = /^(?:от (2[0-9]{3}) до (2[0-9]{3}|3000))?(?:от ([5-9][0-9]{3}|[0-9]{5,})$)?(?:до (1[0-9]{3}|2000|[0-9]{1,3})$)?/;

var m = re.exec( 'до 200' );

if ( m[1] && m[2] ) {
    alert( 'from ' + m[1] + ' to ' + m[2] );
} else if ( m[3] ) {
    alert( 'from ' + m[3] );
} else if ( m[4] ) {
    alert( 'to ' + m[4] );
} else {
    alert( 'Unknown matching' );
}