Which is what the gap is now right? The gap will widen to about 12-15 million by the time the slimlines release, but count microsoft to be aggressive attempting to catch up.
Microsoft may be incompetent, but they will throw money if they have to.
They've thrown plenty of money and I don't think MONEY is the problem here. I'll list what Microsoft has done and why it didn't work.
-Titanfall Exclusivity. This didn't really push it ahead of PS4 because of the XBOs bad word or mouth leading up to launch. Then there's the fact that launching a successful FPS these days is very hard. Titanfall seems to had sold well, for and exclusive but playerbase is not very active with complaints about lack of content.
-Unbundling Kinect. This didn't magically turn the tide because this was an option that should have been there from the very beginning. A lot of the people that didn't want Kinect just ended up getting the more popular, cheaper and more powerful PS4.
-September 2014s Free Game Giveaway with console purchase. The reason this move didn't push it past PS4 was because this was a reactionary move.(like many other of MS's decisions regarding XBO). September '14 was Destiny launch month, heavily promoted and bundled on PS4. XBO really didn't have a chance this month at all. So the free game giveaway IMO was a pretty bad business move as it wasn't going to move the needle and most of your audience would have bought this much-hyped game anyway.
-November "Promotional Price Cut" To $350. THIS ONE ACTUALLY WORKED! The combination of a $350 XBO with a game with the launch of the biggest games of the year and the holidays was a perfect storm. The only problem with this was that Microsoft must have lost millions and millions for these November/December NPD victories and now leading out of the holidays, with the promotional price cut still going on 6 months later they've lost NPD every months so far this year. So you see they won those 2 last months of 2014 but now they're back to square 1 behind the PS4 in sales but unable to go back to "regular" pricing of $399. So they are in the same position as the year before but with much less profit(or possibly losses) per console sold.
The reason Microsoft can't just throw money at this problem and fix it is because the market has already chosen its leader and the only one who can slow down the PS4 is Sony. It's up to Sony to make some big mistakes.