I had made a quick comparison between submission for Rev 2 and Rev 4 as per your request,
The additional price is due to the following
(1) Additional 2 battery breaker (for temporary battery)
(2) Additional DC voltmeter (2 sets)
(3) additional center zero ammeter (2 sets)
(4) additional voltmeter and ammeter (2 sets)
(5) Additional 2 feeders (MCCB) in DB
Due to time constraint, I just make a quick glance. But there are additional things.