'key' meta_query not working custom advanced search (WordPress)

Question

Been trying for hours now and have almost got to breaking point. Tried so many different things but can't seem to get my custom search bar to query results by a pre-defined select price range. I am using Advanced Custom Fields to add the meta tag 'investmentprice' to my custom post type called 'investments'. I feel like it's to do with WordPress not picking up the correct 'key' in my meta_query, even though I have changed this numerous times now.

Here's the code for the config bar:

<div class="config_bar cf">
<form method="get" role="search" action="<?php echo esc_url( home_url( '/' ) ); ?>">
    <input type="hidden" name="s" value="">
    <input type="hidden" name="post_type" value="investments" />

    <div class="col">
        <?php 
            $taxonomy = 'type';
            $args = array( 'orderby' => 'name', 
                'order'             => 'ASC',
                'hide_empty'        => true,
            );      
            $tax_terms = get_terms($taxonomy, $args);
        ?>
        <span class="label_inner">Investment Type</span>
        <select name="type" id="type" class="postform standard">
            <option value="" selected="selected">All Investment Types </option>
            <?php if($tax_terms): ?>
                <?php foreach ($tax_terms as $tax_term): ?>
                    <?php $title = $tax_term->name;
                     ?>
                    <option value="<?php echo $tax_term->slug; ?>"><?php echo $title; ?></option>
                <?php endforeach; ?>
            <?php endif; ?>             
        </select>
    </div><!-- col -->
    <div class="col">
        <span class="label_inner"><?php _e('Select Country','opencloud');?></span>
        <select class="postform standard country " name="country" id="country">
           <option value=""><?php _e('All Countries','opencloud');?></option>
           <?php
           // Display only parents here .
           $terms = get_terms( array(
                // Put your taxonomy name  here.
                'taxonomy' => 'location',
                'parent' => 0, 
                'hide_empty' => false
            ) );

            foreach ($terms as $term){?>
                <!-- We are going to send value for $_POST and data-makeId's TERM_ID for ajax request -->
                <option value="<?php echo $term->slug;?>" data-countryId="<?php echo $term->term_id ?>"><?php echo $term->name;?></option> 
            <?php
            wp_reset_query(); // if you're not in your main loop! otherwise you can skip this
            } ?>
        </select>    
    </div><!-- col -->
    <script type="text/javascript">
        $( document ).ready(function() {
            $('#country').change(function(){
              var $mainCat= $(this).find(':selected').attr('data-countryId');
              if ($mainCat != '0' ){
                // call ajax
                $("#city").empty();
                $.ajax
                (
                  {
                    url:"<?php bloginfo('wpurl'); ?>/wp-admin/admin-ajax.php",     
                    type:'POST',
                    data:'action=get_city_lists_ajax&main_catid=' + $mainCat,
                    beforeSend:function()
                    {
                    },
                    success:function(results)
                    {
                      $("#loading_bar").hide();
                      $("#city").removeAttr("disabled").trigger('change.select2');       
                      $("#city").append(results).trigger('change.select2'); 
                    }
                  }
                );   
              }

            });
        });    
    </script>
    <div class="col">
        <span class="label_inner"><?php _e('Select City','opencloud');?></span>
        <select class="postform standard city " name="city" id="city" disabled>
           <option value="<?php echo $term->slug;?>"><?php _e('All Cities','opencloud');?></option>
        </select>    
    </div><!-- col -->
    <div class="col">
        <span class="label_inner">Select Price</span>
        <select class="postform standard price" name="price" id="price">
            <option value="">All Prices</option>
           <option value="500-1000">£500-£1000</option>
           <option value="1000-1500">£1000-£1500</option>
           <option value="1500-2000">£1500-£2000</option>
           <option value="2000-5000">£1500-£2000</option>
           <option value="5000-10000">£5000-£10,000</option>
        </select>    
    </div><!-- col -->
    <div class="col">
        <button class="search_submit" type="submit">Search</button>
    </div><!-- col -->
</form>

And here's my advanced search query function:

function advanced_search_query( $query ) {

if ( isset( $_REQUEST['search'] ) && $_REQUEST['search'] == 'advanced' && !is_admin() && $query->is_search && $query->is_main_query() ) {

// limit query for custom post type
    $query->set( 'post_type', 'investments' );

// Get query strings from URL and store the min a variable
    $_type = $_GET['type'] != '' ? $_GET['type'] : '';
    $_country = $_GET['country'] != '' ? $_GET['country'] : '';
    $_city = $_GET['city'] != '' ? $_GET['city'] : '';
    $_price = $_GET['price'] != '' ? $_GET['price'] : '';

  if( $_price != '' ) {
    $metaquery = array(
        array(
            'key' => 'investmentprice',
            'terms' => $_price,
            'compare' => 'BETWEEN'
        )
    );
    $query->set( 'meta_query', $metaquery );
  } 

// if type is not empty limit the taxonomy to the specified
  if( $_type != '' ) {
    $taxquery = array(
        array(
            'taxonomy' => 'type',
            'field' => 'slug',
            'terms' => $_type,
            'operator'=> 'IN'
        )
    );
    $query->set( 'tax_query', $taxquery );
  }

// if country is not empty limit the taxonomy to the specified
  if( $_country != '' ) {
    $taxquery = array(
        array(
            'taxonomy' => 'country',
            'field' => 'slug',
            'terms' => $_country,
            'operator'=> 'IN'
        )
    );
    $query->set( 'tax_query', $taxquery );
  } 

// if city is not empty limit the taxonomy to the specified
  if( $_city != '' ) {
    $taxquery = array(
        array(
            'taxonomy' => 'city',
            'field' => 'slug',
            'terms' => $_city,
            'operator'=> 'IN'
        )
    );
    $query->set( 'tax_query', $taxquery );
  }

  return; // always return
}

}

Also, here's a screenshot of the Advanced Custom Field:

Answer 1

Unless there are any other issues, this should be a small fix. You are using the array key 'terms' instead of 'value' in your meta query. According to the WordPress Codex , a nested array of args for a meta query should use value , like this:

$metaquery = array(
    array(
        'key' => 'investmentprice',
        'value' => $_price,
        'compare' => 'BETWEEN'
    )
);
$query->set( 'meta_query', $metaquery );    

Hope that helps..