I can only go by my experience after I realized that my merchandise was really lower than the rest of my league because I had sold off US players and had no homegrown stars. Here's my progression:
11/19/2012 Weekly Merchandise profit $ 15 494
11/26/2012 Weekly Merchandise profit $ 15 870
12/3/2012 Weekly Merchandise profit $ 17 120
12/10/2012 Weekly Merchandise profit $ 15 141
12/17/2012 Weekly Merchandise profit $ 16 403
12/24/2012 Weekly Merchandise profit $ 16 464
12/31/2012 Weekly Merchandise profit $ 16 397
1/7/2013 Weekly Merchandise profit $ 17 563
1/14/2013 Weekly Merchandise profit $ 17 892
1/21/2013 Weekly Merchandise profit $ 16 530
1/28/2013 Weekly Merchandise profit $ 18 322
2/4/2013 Weekly Merchandise profit $ 17 318
2/11/2013 Weekly Merchandise profit $ 18 998
2/18/2013 Weekly Merchandise profit $ 20 411
Notable that I bought a very good US player on 12/31, and the next week i got a $1K bump. I bought another very good US player on 1/12, and within a couple weeks my average started to climb to about $3K more than it had been before either purchase. The $20K week was clearly the best in a long time, and if we sustain that level it would mean a boost of about $5K a week.
I would imagine a guy we draft becoming a star would do even more for us, and I have one trainee in the pipeline who might be a starter in a couple seasons. Maybe as his role increases from bench warmer to rotation player, that will start to make a difference even.