There are various metals that align with planetary energies other than the expensive precious ones like gold. Bronze is a pretty good substitute for the sun if your trying to use the metal for the sympathetic magic element that the metals add. It also aligns with fire magic.
Same with tin for jupiter, copper for venus, iron for mars. If ya dig around you can find similar references. Also another alternative it making wood or stone talismans that can be carved and then lined or leafed with the metal so you don’t need as much.
For example for a sun or moon talisman you could use a stone or wooden disc carve the symbols aligned to your goal into it then apply the appropriate gold or silver leafing to it and then charge it.
Regardie has a good book on talismans that give a few different methods on making and charging them.
If you are trying to use for example the planetary talismans from the golden dawn or solomanic formulas there are shops that sale the metal talismans on base metals that can then be charged with the appropriate rituals but the more work you put into it the more of your energies are invested into the work.
The main point of metals in most talismans is to align it with the specific energies of the planet, element or spirit it is to be consecrated or connected with but there are alternatives to this such as using crystals, oils and incense that align with that specific force.
These elements are generally used as both a tool to help the mind focus and atune to specific energies and for the sympathetic element they provide. Kinda like adjusting a radio to a specific station, the station in this case being the force you want the talisman linked with.