BMW has never tried to be cheap with regard to research; I don't think it's any shocker that they've pioneered a huge amount of new technology we see in cars today, and that includes a large number of engine advancements in the past 20 years. They have always been known as a company that is on the bleeding edge of technology (for better or worse). They've won, what? 14 international engine of the year awards? I was starting to think of a list of things they've developed that have become stadard (like rain sensing wipers, auto fold mirrors, pdc, voice nav, etc... but seriously the list is crazy long), currently there are articles online discussing a hydrogen powered 7 series being tested in Germany.
The reason they went FI is because they have traditionally used inline 6's in the 3 series to maintain the balance they like. Obviously competition has forced them to produce engines with more power, so instead of moving to a V configuration or adding more displacement, they went with turbos. The current TT 3.0 i6 is only 28lbs heavier than the engine currently in the 330i, and it produces 45 more hp and 80 more lb/ft of torque. Not only that but its an all alum crankcase double vanos direct injected engine, it's pretty much state of the art - that is illustrated by the fact that even with the power it achieves it gets respectable gas mileage AND the fact that they have virtually eliminated "turbo lag".
In fact I don't think it's an un-safe assumption that developing the TT inline 6 in the 335i cost significantly more money than it would have cost them to drop in the S54 engine from the M3 or even the N62 V8. Remember, the S54 and it's older brothers (m54, s52, s50) have been producing over 300hp for something like 10 years now. In fact BMW had a 277hp NA inline 6 engine in
1977. It isn't like BMW can't make a high output low displacement NA 6. On further reflection one wonders why they didn't just de-tune the M3 engine and put it in the 335i? It would have been a screamer of a car that would have competed with the IS350/G35 easily. So why didn't they? Because for this application the N54 is the better engine. It's smoother, less track oriented, more of a cruiser engine that competes very favorably. What do you know, they developed a whole new engine when they didn't have to because it was the better engine for the job.
The real question is, why can't Nissan and Toyota make an engine that produces that kind of power without using without resorting to more displacement? Look at the VQ, it's a non-direct injected engine and to reach 300hp they had to sacrifice low end torque. You don't reach peak torque until into the 5000 rpm range whereas the N54 reaches it's 300lbs/ft (30 more than the VQ) at a whopping 1300rpm. The current estimates on the next gen VQs gas mileage as pretty sad... As much as I love that engine (it's an all time favorite of mine), it is long in the tooth and I can't imagine Nissan will be able to string it along much longer.
As for price, BMW doesn't need to be price competative. Infiniti is the one that needs to push value. Until 6 years ago Infiniti was a dying brand; they've had one line of successes and their brand name doesn't exactly garnish a ton of prestige. They are essentially an unknown in the near-lux segment, and it's going to be a long time before they can afford to price in line with MB, BMW and Lexus and still make sales. They manage to remain price competative both because they do a lot of part sharing and are smartly run, and because they have to.
(as an aside, ask this question in a year when the new M3 is released with a V8; the question will be more pertinent then.
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