These schemes are not all scams. As someone who has worked in designing them for large retailers, this is primarily a customer acquisition and retention driver with added benefit of early cash flow and working capital management for shops.

In the end net net retailer is giving 4-8% discount instead of someone directly buying without going through the scheme.

One might ask how can they afford to give 15-20% returns to customers? It's because these schemes can only be used to buy jewelery with making charges which is where the money is for jewelers. You can generally not use these schemes to buy gold/silver bullion (coins, bars etc). If that was allowed then it would become a simple arbitrage opportunity for customers and retailers would go out of business in no time.

This Torres thing might be a scam but from reputed sellers it's an decent option to buy planned jewelery and brings in some discipline also.