Why do I add the Strike Price and the Premium for both the buyer and t...

Let’s say ABC is trading at $50 per share and the option in the question is an ABC Apr 50 call @3.  In this case, the buyer pays the seller $300 per contract, or $3 per share. That also means the seller starts out winning while the buyer starts out losing. How  much? Three dollars per share.

If the stock rises to $51, the seller is still winning. Same thing at $52. What about at $53? At this point, the call option must be worth at least $3 a share. Neither the seller nor the buyer is winning, as this is the “breakeven” point. That means the seller could buy the contract back, and the buyer could sell his contract, for exactly $3—no gain or loss.

So, the seller starts out winning $3 and will only lose money if the stock rises by more than $3. The buyer starts out losing $3 and will only win money if the stock rises by more than $3. If the stock moves exactly $3, both are at the breakeven point, which is the strike price plus the premium for call options.