Ok, but there is also opportunity cost to consider. That $100 could be used to something else, which is even more important thing to consider if money is tight. Of course you might get most or all of that $100 back when you sell your machine. But I like to think that if money is tight, it is tight right now, and things will get better in the future. So that $100 can be much more valuable now than in, say, 4-5 years.
Oh I agree it can be better to save the $100. I'm not saying $100 is nothing, I was just explaining to to you why it's not as easy a decision you makes it out to be.
You basically ask why it's so important to get 8gb of ram, when you can just get 4gb and then upgrade whenever you need to and why it's something that drives so much discussion and thinking if it's that simple.
And I just explained that if $100 is something you need to think about, then that probably means $100 is a lot to you. Which means that selling and rebuying a laptop every 1-2 years isn't an option (unless you're sure you're getting a promotion, as opposed to say getting fired in a year from now). You need to make that decision now.
That's not me saying 'spend $100, it's a no brainer'. I understand there's opportunity cost. It's just me explaining why the decision
isn't a no-brainer, as opposed to you saying 'it's not a major life decision' as if anyone who worries over $100 can just go and buy a new & better laptop a year later when he needs to, as if that's somehow the default position for everyone who worries about $100. Again, doesn't mean spending the $100 now is always the best choice, just explaining where the 'future-proof mania' you talk about comes from.
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If anyone buys a base model from Apple then they need their head examined because they could get that same machine elsewhere for 2-300 dollars cheaper depending on sales, specials and such.
The majority of Apple revenues are from outside the US, so you may want to consider that sales channels aren't universal. For example here in Europe I can get a 10% student discount from Apple, but no other retailer offers it. We also don't get BestBuy movers' coupons, and as Mac products are in high demand, they're usually on the list of exemption to deals like 'pay no VAT this weekend' that retailers tend to run.
So in short, for my particular situation I do indeed buy cheaper from Apple than from other retailers. Surprise. Except if I want to buy last year's model, then it's about the same. But why would I pay equal money for 10% slower CPU/GPU, 50% slower SSD, and a lower resale value, and have to do repairs/warranty etc through a non-Apple retailer, instead of buy from Apple and get this year's model same price?
If I were stateside, completely different story. The deals you can get on e.g. a new MBA 2014 from BestBuy with the right coupon strategy compared to a 2015 MBA is much, much better value. But I hope you appreciate again that most of Apple's revenues and customers are not stateside, and that this forum isn't visited by just US citz.