I'm unconvinced by the cost/time metric. The more you play the game, the smaller the potential difference in cost per hour from original purchase price gets - 30p per hour versus 40p per hour ain't much. Seems like you could always get your money's worth so long as you play enough.
I think it's more useful to compare purchase cost versus game quality. Instead of asking myself 'did I get my money's worth?', maybe 'did the game warrant that cost?' Atm, my answer to that is no. Don't get me wrong, I have enjoyed the game and sunk a lot of hours into it - but if I could've chosen how much I wanted to pay for it, I definitely would've paid less. There's other games that are higher quality for a lower price.