This trophy is best worked on in conjunction with the "A Life Of Crime" trophy as you can work on 2 trophies at one time. Going this route, I found making a separate save (as I was on my "good" playthrough) and just heading into a larger town and pickpocketing everyone netted this trophy in a little over 10 minutes. Didenhill was a good option for me as most people had something to pickpocket but most larger towns are a safe bet. Don't forget to select the "Pay Fine" option each time the guards come for you.
However for those looking for a quicker way on this one, simply murder a few townspeople and when the guards come to collect you, your bounty should be much higher than necessary. Striking (and not killing) a guard is also a pricier bounty over lesser crimes, but according to another guide you will need to do this roughly 11 times before you reach the required amount.