Go to Fiverr, there are many scripts like binance starting at 35 dollars. It is simple php script, you just need a server, also could be found on fiverr price is around 5 dollars per month. 
That's fine if you don't care about security or experience. My team has been building exchanges for over two years. Our projects are of much better quality than what you'll find on any freelancer site.
Doesn't you found it funny, it's just a joke mate!
It's dangerous that people who expect to hold millions in user funds think they can safely do it with some script they paid nothing for. Security takes experience, which costs money.
Also, PHP is a horrible language to build an exchange in.
I agree with you, except for your last point.
PHP has come a long way from what it once was (PHP5 bleh). Every language obviously has pros and cons, but with PHP 7 things are getting better. PHP is an OK language to build an exchange in, just as Python, Ruby, etc are. It's up to the developers and where their skill sets/reservations lie.
https://slack.engineering/taking-php-seriously-cf7a60065329
@OP, if you're not willing to spent more than $1000, don't open an exchange. It's not something you can open overnight with a script. It's irresponsible, as you're essentially opening yourself up to backdoors.