is very high shipping costs are legal?

Is it legal to have very high shipping costs?

The product I am selling has 3 sellers.

He is undercutting me with the price while his custom shipping cost is enormous. And he is winning the buybox.

Product cost 30 usd, shipping 40 usd.

While I sell with Fba but shipping is free.

Is this kind of practice legal? Therotically he can go as low as 10 usd per product, that combined price for him will be 10+40=50 usd