First , whether you dig into the ground or raise it, your base will have to compacted till it reaches the the level depth where you can set on some type of rail to screed your 2 inches of sand and be dead level, or if you want a slope, so your slope is dead constant across the whole area you are intending to put in the India Stone pavers.
Second. I would not put in less than 4 inches of base.
Third ,the ground should be compacted , ideally before you put the base in to be compacted, you MUST know if there are any soft spots.
If you are going to raise it how will you prepare for weather, especially heavy rains and how even railroad ties eventually will decompose at a non-standard rate.
If you use fresh ties, they will last a long, long time but will have to anchored into the in a rock solid form as your ground will first have to be compacted and then your base will have to be compacted and you will be amazed what that pounding can move.
This is not shovel your base in once and then compact and you are done; this shovel in compact , shovel in compact ... till it is level , and I mean if you put a six foot level on it, it reads level, and then you will have to put set down , some form of removable, rails to screed across for your 2 inches of sharp sand.
You diagram shows curved edges and put pavers in around curves mean hours of cutting stones to adapt to that that and makes lay edging pavers far more time consuming.
When I did this for a living, I could lay a 20 by 20 ft. square area in a matter of minutes; if there multiple objects in that 20 by 20 area to cut around that amounted to hours of cutting.
How much it costs to excavate depends on the area you live in, how easy is access to the area to be excavated, and where to put the removed substance.
This is an area that is 33 by 30 feet , does every thing in your drawing fit into that small area?
