"Fact is that $1 today is a different commodity than $1 two years from now. Assuming a market rate of 10%, that first dollar is worth $1.10 two years from now. Keep adding these up and you'll soon learn that $419 today is the same as $459 in two years (give or take). 419*1.10 = 460.9"
Well, sure, if inflation is really that high. CPI has gone up that 9.5% in the last 4.5 years, so you are probably more than double counting inflation.
Tack on that I can get 1 year of XBox Live Gold for $50 from Target, Walmart, etc and the XBox for $275 from Target.com, it is really $375 vs $459, a 22.4% difference-- which is more than inflation over the last 8 years...
Figuring 3% inflation, in today's money it is $375 [assuming you buy two of those $50 subs immediately to 'lock in' the price] vs $449.
If you happened to have a way to invest the difference, at 26.5% annual interest, then you are roughly break-even with inflation included. Granted if you did, then you would have so much money you'd probably be buying a gold plated and diamond encrusted XBOX [or atleast the 250GB version

]
There were rumors that it would also include a '$50 value' two year warranty, which would have brought the two closer, but then again, Target offers a three year warranty for $29.
There were other rumors that Netflix and/or Hulu Plus would also be included. Like with the warranty that would have helped atleast make the deal moderately justifiable.
I would vote for save $20 per week, for the next 11 weeks and just buy the thing outright [with one year of XBox Live]