What is a castable gold-coloured metal that is less expensive than gold?
Maybe you could use epoxy resin instead of metal. It's not exactly cheap and you'd have to do some research as to which resin is best suited for your purpose (or suited at all), but there are tons of YouTube videos of how to design tables with epoxy.

The coloration could be a problem because depending on the pigment it won't look like metal at all, even if the pigment is golden. If you want to take this approach, I propose you buy colored resin instead of coloring it yourself.

If you're interested in epoxy resin, you should research the following topics before executing your first project:


The different kinds of resin and their properties. Some are only suited for thin layers, others only for thick layers. If you use improper resin, it might stay soft and sticky.
The safety measures! Always wear goggles and gloves and keep the area well ventilated, even if you don't smell any noxious fumes.
How to get rid of bubbles. This is a common problem with resin but less severe with opaque colors.