Well the domain is the number of tickets and the range is the cost for those tickets.
So x = 1 when y = 125 (1 ticket is 125 dollars). Here is a reasonable domain and range comparision:
x = 1 , y = 125
x = 2, y = 250
x = 3, y = 375
x = 4, y = 500
ect...
The lower limit of the domain is 0 because you cannot have less than 0 tickets.
I hope this helps!