i went through all this last week i went shopping for a brand new trailer for my 5.3 mtr runabout and well braked trailers start at around the $2400.00 mark for a 16" trailer and thats only going up by couple hundred for the size for 14-15" ones were around the 2200 mark braked
if your in sydney there are 2 places i can suggest to call and get quotes they were the cheapest for my self, ill pm them to you if you want.