Get unique post by meta value using wp_query

You can simply limit the query to return only one result. To achieve this, use the field posts_per_page in your query arguments. Check the documentation for more info on this.

$args = [
    'cat' => '44',
    'posts_per_page' => '16',
    'post_type' => 'post',
    'post_status' => 'publish',

    'meta_query' => [
        'metavalue1' => [
            'key' => 'Meta_value',
            'value' => '',
            'compare' => '!='
        ],
        'price1'=> [
            'key' => 'price_euro',
            'value' => '30',
            'compare' => '>',
            'type' => 'NUMERIC'
        ],
    ],

    'orderby' => 'price1',
    'order' => 'ASC',
    'posts_per_page' => 1,
];

$wp_query = new WP_Query($args);

^{Sidenote: To make your code more readable, try to stick to one thing. Using short array syntax ([ ]) somewhere? -> Use it everywhere and avoid array(). Using 'key' => 'value'? Don’t use 'key'=>'value' somewhere else.}