You would have heard similar arguments during the fight for labor rights in the early twentieth century, to wit: if you want to pay people a living wage you won't be able to have all the products you enjoy. However, the labor movement won and as a consequence we went on to have a thriving middle class in addition to an explosive economy through most of the century that followed. So I don't take these "common sense" economic arguments at face value: there is generally another solution that defies this "logic". In terms of animal treatment, sure if we rely on our current model of factory farming, eggs will be more expensive "sans cruelty". But two points, First: does that mean we should continue with the cruelty? Second: under a different food supply model this isn't necessarily true -- e.g. in developing countries poultry is produced very differently: that is, there are just chickens running around everywhere eating the stuff off the ground that humans drop. there are no warehouses full of chickens, but still lots of eggs and chicken. So if we really wanted to we could probably think of a better way of doing things and still keep prices down.

However, while it's not possible to predict exactly how, in general, if we keep packing people on to the planet and everyone keeps reproducing like there's nothing wrong, then something is going to give -- our food supply system will fail (it already has if you consider a working food supply to not feature mass amounts of animal cruelty), our planet's dynamic ecosystems will be reconfigured (in a manner probably inhospitable to humanity), natural resource will be depleted, etc.