This is a popular method for Sony Xperia users, though it yields mixed results regarding the actual bootloader status.
Usually ranges from $20 to $50 depending on the device model. 2. Chipset-Specific Exploits (Dirty COW, MTK-SU) docomo unlock bootloader top
Older flagships vulnerable to EDL (Emergency Download Mode) leaks can sometimes be flashed with modified firehose programmers to remove lock flags. 3. Cross-Flashing Global Firmware This is a popular method for Sony Xperia