Best option for retaining wall

Hi guys!

I need help with my retaining walls, I need to decide what is the most cost effective way of retaining large banks.

I have sandy soils with very good drainage, but here in my subtropical climate, timber of any kind is not an option, my timber walls are totally rotten and full of mould, termites and bora, it's a mess.

I have one very large wall (50m long by 2m high) done with D-block concrete retainers and I must say I am very happy with them, they don't budge and after plants grow on them they aren't too ugly.

But now I need two more walls done, if I use D-block I will need 1200 of them which is expensive!! I was wondering if anyone has had experience with the Loffelstein block or interlocking block, is it a more cost-effective option?

Hope someone can help?:huh: