Last year in May when we were staying at the Sheraton Suzhou, we arranged for a ride from the hotel to my Shanghai hotel (on the Pudong side) thru the travel agency shop in the Sheraton. I paid RMB 450. During our ride there, my wife asked the driver how much would his company charge for a ride PVG<=>Suzhou if we booked it thru them (the transport company, not the travel agency) directly in the future. He said RMB 300. BTW, our taxi metered ride from PVG-Sheraton Suzhou last year cost around RMB 575.

So if you're interested, here's the transport company's phone in Suzhou:

Office: (512) 6209-0140
Cellular: 13901545540
Owner's Name: Mr. Huang

Employees don't speak English so you'll need someone who can speak Mandarin. The car we rode in was pretty new and cleaner than the taxi from PVG.