You're hitting the wrong URL. Instead, hit the AJAX query one inside it and parse it as JSON:
$f = file_get_contents(
"http://steamcommunity.com/market/search/render/?" .
"query=booster&start=10&count=10"
);
$t = json_decode( $f );
print_r( $t );
And you get a neatly organized structure, such as:
stdClass Object (
[success] => 1
[start] => 0
[pagesize] => 10
[total_count] => 330
[results_html] => <div class="market_listing_table_header">
...
Essentially the JSON file that's used to render the page can be read as a neat structure in PHP. Or close enough. You'll still need to walk through $t->results_html
with DOM Document / XPath for further parsing.