How to create these plots?

That's probably what you're looking for.

documentclass[tikz,export]{standalone}
usepackage{pgfplots}

tikzset{
    declare function={
    CallMatu(x,KK,Prime) = max(0,x-KK) - Prime ;
    PutMatu(x,KK,Prime) = max(0,KK-x) - Prime ;
        }
}

pgfplotsset{
    BSMatu/.style= {red,line width=1.8pt},
}

begin{document}

defKK{100}
defPrime{5}

    begin{tikzpicture}
        begin{axis}
            [
                xlabel= Underlying price $S_{t}$,
                ylabel={PnL at maturity},
                domain=0:200,
                samples=101,
                axis on top,
                axis line style={black!40},
            legend style={at={(0.5,1)},anchor=north, draw=none}
            ]                           
            addplot[BSMatu] (x,{CallMatu(x,KK,Prime)});
            addlegendentry{Call pay-off at maturity}
%           addplot[BSMatu] (x,{PutMatu(x,KK,Prime)});
%           addlegendentry{Put pay-off at maturity}
            
        end{axis}
    end{tikzpicture} 
    
end{document}

It is very simple with pstricks. Here is an example with the first plot:

documentclass[svgnames]{article}
usepackage{pst-plot}%
usepackage{sansmath} 
begin{document}

    begin{pspicture}sansmath
    psset{unit=2cm, linejoin=1, showorigin, ticksize=-3pt 0.4pt}
    psaxes[Ox=50, Dx=50, dx=1, Dy=5, dy=0.4](0,0)(2,0)(0,4)
    uput{8pt}[d](0,0){$ 50 $}
    psline[linewidth=1.2pt, linecolor=IndianRed](0,0)(1,0)(2,4)
    end{pspicture}

end{document} 

You can use the pgfplots and tikzpicture packages, and then set up all of the individual conditions of the graphs (e.g. the axes, the axes labels, and the numbers on the axes and their frequencies).

Although you could plot the individual points, these graphs seem to be linear, so you can just find the equation for the line (using a little point-slope form) and then plot them on the graph.

More information here: http://pgfplots.sourceforge.net/pgfplots.pdf