The economics of the cell – the way scarce resources are allocated – is an important factor defining what are the genes being expressed at a given time. Using Escherichia coli as a model, we have quantified couplings in the expression of two reporter genes arising from limitations in, mainly, the translational machinery. As a result, the expression of the genes is constrained by linear manifolds named ‘isocost lines’, a term inspired by microeconomics. We have used these lines to determine, both in experiments and simulations, factors controlling the couplings such as strength of ribosome binding sites and copy numbers of the genes involved. These couplings are largely dependent on the environmental conditions and, in an attempt of understanding them at a global level for potential applications, we are currently integrating whole-cell metabolic models with multi -omics data.