How can I avoid transparent rendering if I use png sprite sheets?

I am using PNG sprite sheets and they all have transparency around each sprite.
I packed all my sprite with Sprite Packer.

When I use my profiler, I see that Transparent rendering takes up 95% of the rendering (opaque only 5%)
It seems that transparent rendering is more expensive than opaque rendering, so I would like to reduce it.

How can I solve that problem, given that my sprite sheets have transparency?
Should I have to make a mesh around all my sprites to avoid the transparent pixels?

Thanks in advance

Unity Pro can create tight meshes around sprites in order to reduce overdraw.