Thinking about it there aren't many things that are as cheap an durable as steel and aluminum. You surely know how the amount of energy you get out of the panels changes with inclination and just laying them flat is only feasible if you aren't concerned with that loss per unit of energy output or your plant sits on the equator. But in that case you can massively simplify the mounting system and raising the panels up would make maintenance from below easy.

It doesn't feel like masonry or poured concrete walls will be a much cheaper substitute either. Wood might do in arid conditions with well behaved weather but you may pay in maintenance over time what you save at the start.

I think a better approach is to improve the yield per unit with either better panels (split-cell bifacials currently seem to offer a nice bonus in yield just from back-reflected light) or some other thing you can do to improve overall profit per unit land.

Of course there are situations land is so cheap it doesn't matter as a cost factor but after a point you would pay more in other infrastructure than you save again.