I was in Cochi 2 weekends ago, throwing in my 2 cents.
In my view Fort Cochin and surroundings IS a backpacker's place with many homestays (some shady, some very nice-looking), 2-3 stars small hotels and decent restaurants. If you are looking for something more "posh", there are some expensive hotels , but I would not go to Cochin to spend >300$/night for hotel...