(b) For the purpose of the proper administration of this article and to prevent evasion of the tax hereby imposed, it shall be presumed that all conveyances are taxable. Where the consideration includes property other than money, it shall be presumed that the consideration is the fair market value of the real property or interest therein. These presumptions shall prevail until the contrary is proven, and the burden of proving the contrary shall be on the person liable for payment of the tax.