The chances with 500/max number of tickets is higher, but there were also winners in the last two lotteries which have only bought a few tickets (as low as 10). The top prize of the last two lotteries was won by people which have not bought the maximum amount.
Around 200k tickets were bought by 2k participants. Average number of tickets per person is around 100. Each ticket gets a number, 101 numbers are randomly picked and those are the winners.