Well, numerically valid, but the thought is wrong as it means the items are equal-- the car for $10,000 may bring much more happiness than the lunch for $10... most likely.
Money really can't buy happiness-- it's true. It can make life easier, but the only reason that having something is good is because you didn't have it before. You're not really all that happy that you have air-- sure, it's needed and you'd be mighty unhappy without it, but it doesn't cause happiness. More than anything else, it's the most wonderful and needed thing-- having air should make us happy all the time. But once we have it, it no longer is all that special. Just like anything, even a really expensive new car, life has a weird way of working, where the grass is always greener on the other side of the fence-- has to do with boredom and hope, I suppose.