gear selector stiff n hard when shifting from park to reverse and viceversa

I have a 2000 corolla with an automatic transmission and about 115500 miles on it. The problem that I have is that the gear selector feels really hard and stiff when I have to shift from park to reverse and viceversa. Other than that the transmission is working pretty ok - as soon as I move to reverse/drive it engages quickly and without any jerks. Any ideas on what could be the problem with the gear selector and how much it would cost to fix...

Thanks for your help!