It wont work.....
Eschew material only works for spell that don't have a costly material component....
Similacrum has in addition to needing a part of the creature a component of at least 100 gp(ruby).....
Of courswe you could always use wish or miracle or dwermokeeper's supernatural spell to bypass needing the component ......
Eschew Materials [General]
Benefit
You can cast any spell that has a material component costing 1 gp or less without needing that component. (The casting of the spell still provokes attacks of opportunity as normal.) If the spell requires a material component that costs more than 1 gp, you must have the material component at hand to cast the spell, just as normal.
I don't really see that it excludes using it on spells that have both a costly component and a "cheap" one.
Let's for example take Simulacrum. It has both a costly material component, and one that costs less than 1 gp. Then let's break down each sentence of Eschew Materials, and see if Simulacrum qualifies.
1)
You can cast any spell that has a material component costing 1 gp or less without needing that component.Does it have a material component costing 1 gp or less? Yes. So we can cast it without that component.
2)
If the spell requires a material component that costs more than 1 gp, you must have the material component at hand to cast the spell, just as normal.Does it have a component costing more than 1 gp? Yes. So we still need to use that component.
I don't see why this wouldn't work... unless you argue that a piece of a creature has a monetary value.