Hi,
I have seen the Etsy clone script from Agriya and I see that it has most of the the features you have requested, but not all. For instance,it does not have the option of choosing cutom product templates. Although it has an option of multi-store, it does not allow you to customize the store template like eBay. Also, the etsy clone script does not seem to have an ad management platform. But on the brighter side, it does have most of teh crucial features such as adaptive payments, internal messaging etc.
So even if you use an off the shelf solution (agriya or anything else), we will still need to custom code a lot of things. However it would be cheaper than scratch development.
To give you an idea....
For a complete custom development of all features and modules, the cost would be around $7500 to $ 8000at a timeline of 75 to 85 business days with testing. However if you use an off the shelf script and we add in the missing modules or customize the existing modules, the cost would be around $3500 at a timeline of 40 to 45 business days with testing.
Therefore what I suggest is this.....
If you wish to go with agriya script, please go through the demo and let us know regarding the customization you with to implement. If you wish to go with a custom solution, please send a list if features and modules required (user side and admin)
Ultimately it all boils down to what your budget is.
Look forward to discuss further,
Thanks,
Prasun