The comparative form of an adjective

[Shamsiyan]

Look at the following sentences.

Tickets were less expensive than I had expected.
Tickets were not more expensive than I had expected.
Tickets were cheaper than I had expected.
Tickets were not as expensive as I had expected.

I want to know whether these sentences have the same meaning? (I think that they have the same meaning.)

[Grumpy]

"Tickets were not more expensive than I had expected" is very clumsy, and should not be used. It could mean either that tickets were "as expensive" or "less expensive".
All the rest are perfectly acceptable, and mean the same.