You say that titanium and adamantite are too expensive, but they're actually much quicker to upgrade to then the second metal, tin.
With copper at 10$ and tin at $500, you need to sell 500 ingots worth of copper to reach tin. (not including grips/guards) After that, you only need to sell 20 ingots of tin for iron (at $1000), 50 ingot ofs iron for adelite (at $5000) and that cycle repeats. (Unless it's changed since I last looked.)