For instance, considering just a 100% atk multiplier (auto attack?):
If you are hitting with 1000 atk versus a 500 def enemy, it will result in a 430 dmg hit.
If you increase your attack to 2000 atk (transcendence 5) it will result in a 1200 something hit, wich is about 1.5x the original hit (transcendence 5 is 150% atk now so… you get it).
If you increase your attack to 3000 (transcendence 10) it results in a 2130ish hit, wich is about 5 times the original 430 hit (transcendence 10 is currently 550%).
Overall it doesn’t change transcendence power that much. Transcending your weapon to very high levels will result in tremendous damage increases.