Seems like a crazy number at first, but it isn't nearly as hard as it first seems. Once you get a faster car and unlock the Driftkhana levels, getting 2 million is pretty easy. Getting 5 million isn't even that much of a challenge. Unlocking this trophy will also get you "Multiplier Master" as you will need to get a high multiplier in order to get the trophy.
Pick a level from Driftkhana that you are most comfortable with. Find the best donut spot and just keep drifting around this spot. You will get a lot of points just from the drifting and then get a nice bonus from the donut ever few seconds. As the multiplier goes up with will be getting 10k+ for each donut you complete while still getting a huge amount of points from the drifting. If there are boxes nearby, wait until you are at least x10 on the multiplier in order to get 1000 points for each box. The near miss poles are a risky one to go for as you can easily hit one too hard and break the multiplier. Focus on the drifting to make it much easier to get this.
You can definitely get this with the starter cars, but if you are having a hard time, wait until you have the hoonvan and this should be even more easy to get.