Most cost effective way to test USB 3.0 eye diagrams
BeB00, unfortunately you are sorely mistaken underestimating the challenge. The USB 3.0 eye qualification requires at least a 6 GHz scope, which will bring you into ~$75k area. 

More, if you mean a wider USB 3.0 qualification, the price tag is substantially higher. To begin, you will need a set of RF-grade test fixtures, which will run into additional $15-$20K. You will need a special signal generator (~$100K) to test LFPS signaling, BERT system (~$150K), protocol analyzer (another $25k), and a set of certified (USB-IF approved) devices. Last time I recall the bill was approaching $0.5M mark.

ADDITION: To evaluate USB 3.0 signals (eye diagram), you must have a qualified oscilloscope with DSP capabilities and corresponding software installed. Old direct methods don't work because the signal eye is typically closed at the far end of transmission link, sometimes completely, as this Teledyne/LeCroy article illustrates on PCIe example:



and the receiving device (scope in this case) must use CTLE to open it, which implies a continuous sequential sampling of signals.