Insurance is generally governed by statistics, and if you look at the stats a 125cc motorcyle is at greater risk of being stolen than a larger cc one, people tend to cherish the larger bikes and give them better security, 125's are on the whole a stop gap and not usually as cherished, therefore security is at best basic and quite easily bypassed, therefore premiums are higher, and highest of all in the crime hotspots, London being the major one, but most cities will have a high percentage of bike related thefts compared to minor villages out in the sticks, but until as such time as these thieving scum are sentenced appropriately and made to pay properly, it will only continue to get worse