Would you refactor this and if so, would you charge your client?

Question

I am working on a freelance job at home. The client wants me to write some new functionality for his CMS, but it is taking me a lot of time to figure out what the code is doing, because it is written in a very unreadable style.

Below is just an example of what I mean. The previous programmer made extensive use of anonymous functions, of eval(), he uses deeply nested ternary operators, he didn't indent code, didn't use comments, and he uses funny constructions like misusing the behaviour of logical operators || and && for creating if/else conditions (the second condition of && only gets tested if the first one is true, opening the possibility to use && as an if/else construction). All in all it's insane code and it's costing me a lot of time to find out how the current code works.

return ($this->main->context != "ajax" || in_array($this->type, $this->definition->ajax)) ? eval('return method_exists($this,"Show'.ucfirst($this->type).'") ? $this->Show'.ucfirst($this->type).'('.(count($args) ? join(",",array_map(create_function('$a','return (is_numeric($a) || preg_match("/^array/",$a)) ? $a : "\"".$a."\"";'),$args)) : "").') : null;') : '';

Would you refactor this code and how would you handle this sort of thing with your client, I mean financially?