Suppose GetThere Airlines increases their ticket price to $200+10n = 10(20+n)$ dollars. Then the number of tickets they sell is $40,000-1000n = 1000(40-n)$ . Therefore, their total revenue is
$10(20+n)\cdot 1000(40-n) = 10000(20+n)(40-n) = 10000(800+20n-n^2).$
This is maximized when $n=-\left(\frac{20}{2\cdot(-1)}\right)=10$ . Therefore, they should charge $200+10\cdot 10 = \boxed{300}$ dollars per ticket.
