For a safety razor, you can get 100 voskhod/rapira chrome/astra green (razor blade inserts) for $11-14 AUD delivered, which last around 3-6 shaves depending on your stubble. The razor itself, you can buy a good razor (merkur 34c or edwin jager de89) for $40-60 delivered, and will last years if cared for. So you can shave for a whole year on $15-20 if we remove brush and soap (which are consistent between cart and double edge, and should be using a good soap/brush anyway as it's the cheapest way to a better shave with either cart or safety razor).
For a soap, let's say $20/125g, you should get about 90-100 shaves (unless you load like some of the people here
, average per shave for a normal person is around 1.2g from what I've seen), which would work out to around $1.40/week for a great shaving soap. You can pick up a great synthetic for $30-40 AUD delivered, which again will last years. So, for the price of a can of coke a week (or other vice), you can have much more enjoyable shaves, turning something monotonous into something fun.
*caveat - as with anything on this forum, it's entirely dsdf (different strokes for different folks). This is merely my experience and thoughts