Required GBW of an op-amp
Study the blue line (a half-decent op-amp's open-loop gain) in the picture below: -


At 10 MHz the gain is unity (0 dB) hence the GBP is 10,000,000
At 10 kHz the gain is 60 dB and, a gain of 60 dB is 1,000 hence, the GBP is 10,000,000
At 10 Hz the gain is 120 dB and, a gain of 120 dB is 1,000,000 hence, the GBP is 10,000,000

So, this op-amp has a gain-band-width-product of 10,000,000 and if we wanted a closed-loop gain of 34 dB (a gain of 50) we can draw the purple line and see where it intersects the blue line. In this example, we can see that it is 200 kHz and, not surprisingly that means a GBP of 200,000 x 50 = 10,000,000.
If we expected a band-width of 1 MHz we wouldn't get it with a gain of 50.