Okay lemme put it, I've worked in apparel sector for a long period of time and during this I've liaised with Ecom retailers like FK, Myntra & Amazon while working with apparel manufacturing brand(including shoe companies). As long as I was in the that sector (Until late 2016) there were no formal way of limiting an ecom retailer to stick with 'our discount' model. It's only on a mutual basis/ best effort basis. Legally if the brand tries to arm-twist the ecom portal or threatens to discontinue supply based on this, it will constitute an offence.
Second, there are supply of kinda inferior shoes (not necessarily inferior but certainly corners cut in manufacturing) , produced in India or at some other low cost center and ecom retailers bulk buy these styles as their bread and butter model. Even in stores you have sections where shoes will be economical/heavily discounted but workmanship/quality will be a tad off. Look at the merchandise on lower shelves.
Third, over a period of time, old style SKUs get accumulated and they are sent to factory outlet/smaller trade outlet shops in smaller cities/ around highways at a throw away price sometimes in flat rate against number of pairs/weight. Cost per pair in these lot can be as low as Rs 300 a pair against something that might be marked at 6K or even higher.
Fourth, its only third party resellers that will have fakes and there's a very very slim probability of fakes making into official seller's inventory unless it gets mixed up at some warehouse/ staff collusion which isn't that common or at a scale which can be perceived to be serious problem.
I haven't been in this sector for long time but if needed I can get further clarification if someone is curious.