Just throwing it in there as a possible reason.
Warning: The following about recycling is very anecdotal and very localised, so please take with as much salt as you desire
A friend of mine is "da top dog" of a local recycling centre, which covers a population of around 300K. The part of the centre he is responsible for is the "drop in" element, where householders such as myself can take grass, bottles, wood and any other household waste for.... recycling
A huge element of what we householders drop there are white goods (washing machines, freezers, cookers) and electrical appliances.
There's a surprising amount of desktop computers, monitors, tv's, dvd players, home cinema systems and laptops taken for recycling.... many times in good working order. But almost never will they see a game console, with the rare exception of the odd Wii (sans peripherals).
Why this is, I don't know. I'm guessing that most either have them repaired (under warranty or not) or possibly just stick them away in a cupboard. The difference between a console and a TV is that the consumer is invested in the console, usually to the tune of hundreds and hundreds in software and other peripherals, making a repair more attractive than dumping it.
Sure, some of those consumers will look at a replacement. But I'm guessing that the vast majority of owners, on turning on their PS360Wii and discovering it doesn't work for whatever reason, will end up on the phone to the relevant support line very quickly, rather than just chuck it and go to the nearest shop and get a new one. The reasons are many, but I'd say the main one is that their purchases and saves are in that box and they want it fixed.
Which is why, even if most consumers aren't aware of the 3 year warranty, when they call with their E74 or whatever they will be told, or if they go to xbox.com support the first question asked is about RROD/E74.
Which brings me onto your point about straight swap. Yes, some retailers will do this if the product is still within the normal warranty period. However, in the grand scheme of things that new console won't count as a new sale. The swapped product will go back to MS, where it will either be reused as a refurb in one of their repair centres, or scrapped if beyond repair (as will any coming into their repair centres). A returned product that isn't reused will be counted as a negative on their balance sheet for auditing purposes. The same for Sony, et all.
Eg: Month 1 - 100 console sales, 10 of which are faulty and returned will still show 100 console sales for month 1, However, if there are a further 100 console sales in month 2, it will show as a net of 90 console sales, therefore coming to the true figure of 190 sales over 2 months. This is only relevant for warrantied products though, as once outside warranty repairs/replacement are chargable and hav no material financial impact on the manufacturer.
All of the above being reasons why I feel it's not so easy to assume certain consoles have more paid replacements than others, especially when one considers that most "bad" 360's are likely to fail within that 3 year warranty period and essentially become a zero sum statistic in terms of console sales.
