Note that some of these approaches are not legal in the EU and rules in the markets for some products such as TVs that discussion of MSRPs or RRPs (Recommended Retail Prices) can be an indication of price fixing. ERPs (estimated retail prices) need to be used for internal forecasting ideally gathered from respectable information services such as GfK and if the ERPs were all €x99 that would be suspicious. Routinely asking retailers what prices they were selling at could be grounds for an investigation.

One approach sometimes taken (although I suspect not by Apple) is that if one retailer discounts the product the manufacturer supports other retailers to match the discount. This is illegal in the EU as it acts as a deterrent to any discounting as it will get the initial discounter no benefit (market share still ends up shared but they unlike their competitors have to pay the cost of the discount).

Despite this Apple maintain tight control of the prices probably by thin retailer margins with money made up by accessory sales and probably some support/discount/payments for retailers who display Apple products according to their guidelines. It is allowable to offer different terms for different types of retailer e.g. dedicated Apple store, store with dedicated area with demo units complying to guidelines or online although it should be non-discriminatory in that any company that sets up to comply with the terms should be allowed.