I am agreeing to your view that perception is not always transferred to higher brand equity. But brand equity is the added value endowed to a brand, that is through consumers attitude about positive brand attributes and favorable consequences of brand use. So that positive association may lead to brand equity and the negative association may lead to negative brand equity leading to liabilities.
We define Equity into Firm-Based-BE; Employee-Based-BE; Customer-Based-BE (attached), and all three must be aligned, i.e. customer perception (Image) with internal desire (Identity) and reality (Soul).
While BE can originate from many sources as already depicted by comments here, the key answer would be that positive perception is expected to have positive impact on BE, only when positive perception (along with other marketing mix) would have positive influence on customer behavior. For reference, you can read the attached article by Kevin Lane Keller, pages 7 and 8. Hope it helps.
coming to the point to perception it will differ from person to person. if we made the customer satisfied with our products/ service. he will get trust, once he get trusted over the shop/brand/products/service it turns to loyalty. once the customer become loyal to the company/product. he will do the regular transactions then it will leads to brand equity. so how much the customer precept the product/service that much equity will improve.
sir this may be lengthy one but i felt that is written. i think this will give some picture on that.