The main difference you will notice is that the more expensive boots allow you greater mobility of the foot from the first day of use, while the economic ones will need several days riding on a motorcycle so that the skin softens.
This is because the high-end models use a higher quality skin, so it can be thinner with the same resistance and they usually combine it with ankle joints integrated in the plastic parts.
A high-end boot is lighter and gives more control over the brake pedal and shift lever.
In terms of protection, all models provide a similar level of protection.
The reference brands are Alpinestars, Gaerne and Sidi, while other brands such as Fox or Thor have products at a level slightly lower than the first.