In fairness, P&O certainly weren't our first choice but getting my wife, my son and I for £1,100 including flights and luggage in January to Canaries seemed like a no brainer. I think I'd be lucky to get flights, luggage, transfers and full board at a reasonable hotel for anything like this money?
When you say you got the AI for half the price...I'm presuming you're not talking ~£550 and instead your cruise budget is a good bit more than ours? Luggage alone seems so expensive now when flying and with a wee 3 month old unfortunately I can't go just hand luggage anymore.