More, like people who buy with the "intent" of going SLI "later on", few actually do. The majority of SLI systems are built as SLI from the get-go. While a lot of hardware junkies are gamers, the reverse isn't necessarily true.
So many of them are looking to get the best possible system NOW, and not have to fart with upgrading in a year and a half if the system they build remains acceptable (barring simpler things like video card upgrades and more memory) for a 2-3 year time-span.
As I said earlier, the best upgrade path is one where the system remains in the "acceptable" range so long that you don't NEED to upgrade it before it would make better economical sense to just replace it.
I don't buy with the intention of a "massive" upgrade later. I buy with the intention of giving it a GBP£200 upgrade 2 years down the line. My machines have a 4 year lifespan. I buy something that'll run everything I throw at it now. Moving from the old rig 9650/4Gb/GTX260 to the FX-6100/8Gb/MSI 6850 Cyclone cost me GBP£350 in the shop. Mainly because I set a flat budget for the upgrade. After rebates it's cost me GBP£305. Sure I could have burned £500 on it right now, but I've always biught a basically decent machine, and upgraded it 2 years later. Be that more RAM, a new GPU, or a new CPU (Last machine actually got a CPU and GPU upgrade from a 6000+ and a 2900 Pro to the 9650 and GTX260). Relatively minor upgrades, and didn't cost me a huge amount (£170ish IIRC). Also on the original purchase of the 6000+ the bang-for-buck was MUCH better with AMD than the old E6400 that came in the same price bracket.
Likely the Mid-Life update will be a new CPU and GPU, and I don't see anything other that I'll need for 4 years at least. The old rig was still acceptable for the most part, what drive me over the edge was the constant "The display driver NVxxxxxxxx has stopped responding", and has also meant that after the THIRD nVidia card in a row that I've owned has been a pig I'll never buy their stuff again.
I considered an i5 2500, but as I was working to a set budget it just didn't fit for me. The AMD CPU cost £90 after the rebate, and that's bottom end i3 money over here. Even a few months down the line the 2500 rig would still have bumped the build by a MINIMUM of £125 after adding in a similarly specced board (i5 2500 was around the £150 mark still, and a similarly specced board at the time was £120ish). That's in opposition to a board, CPU and RAM package that cost £245 in total. Yeah I've "lost" some performance, but the extra performance wasn't worth the extra cost.
No, it means you get a Good Enough system now, that does everything you want, and doesn't skin your wallet. I've not found anything that this setup doesn't run more than acceptably, and don't TBH expect to find anything for 18 months or so that will bother it.
I also work with many different systems on a daily basis, and I have to say that the Bulldozer isn't as bad as the benchies, and the fanboys suggest. It's not amazing, but it's Good Enough for anything you'll do now.
Marginally more expensive?!
FX-6100 = £112-£15 rebate = £97 at the moment, and the the i5 2300 is £142 (checked on Scan.co.uk). That's not a marginal cost, that's nearly half as much again.
Basically as I spend £500ish over a 4 year period I will end up in 2 years with something better than the i5 2500 is now. If I dropped an i5 2500 in to my machine it would have upped the cost, and meant no GPU for Beaker (when I set a budget it's a HARD budget) until the MLU , and the GTX260 really wouldn't have cut it by then.
If you want maximum bang for your buck, and want it now cudos to you, however us mere mortals are quite happy to get something that does what we want NOW, and upgrade it later if it's required.