Under Settings>Categories there's an option called Enable / Disable the price field, which can hide the price field on certain category listings. This works well. But when editing such listing in dashboard, the fields are visible. I think they should be hidden here too, because it creates a lot of confusion when they're present.

In "dashboard" you mean in backoffice?

In "dashboard" you mean in backoffice?

Yes.

@morfik
Prefer to have more options in backoffice.
See your point but right now not sure...

But since the fields don't apply to the listings, why just not to remove them? They have no purpose in such listings and only confuse admins/mods.

It's going to be blank. What would be confusion?

Because of their existence. If they have no purpose in some listings, they shouldn't exist there -- the principle is the same as with other fields.

I changed this:

<fieldset class="s4">   
        <h2><?php _e('Price', 'beta'); ?></h2>

        <div class="in">
          <!-- PRICE -->
          <?php if(osc_price_enabled_at_items()) { ?>
            <div class="price-wrap">
              <div class="inside">
                <div class="enter<?php if($price_type == 'FREE' || $price_type == 'CHECK') { ?> disable<?php } ?>">
                  <div class="input-box">
                    <?php ItemForm::price_input_text(); ?>
                    <?php echo bet_simple_currency(); ?>
                  </div>
                  <div class="or"><?php _e('or', 'beta'); ?></div>
                </div>               
                <div class="selection">
                  <a href="#" data-price="0" <?php if($price_type == 'FREE') { ?>class="active"<?php } ?> title="<?php osc_esc_html(__('Item is offered for free', 'beta')); ?>"><span class="isTablet isDesktop"><?php _e('Free', 'beta'); ?></span><span class="isMobile"><?php _e('Item for free', 'beta'); ?></span></a>
                  <a href="#" data-price="" <?php if($price_type == 'CHECK') { ?>class="active"<?php } ?> title="<?php osc_esc_html(__('Based on agreement with seller', 'beta')); ?>"><span class="isTablet isDesktop"><?php _e('Deal', 'beta'); ?></span><span class="isMobile"><?php _e('Check with seller', 'beta'); ?></span></a>
                </div>
              </div>
            </div>
          <?php } ?>               
      </fieldset>

to this:

<?php if(bet_check_category_price(osc_item_category_id())) { ?>
      <fieldset class="s4">   
        <h2><?php _e('Price', 'beta'); ?></h2>

        <div class="in">
          <!-- PRICE -->
          <?php if(osc_price_enabled_at_items()) { ?>
            <div class="price-wrap">
              <div class="inside">
                <div class="enter<?php if($price_type == 'FREE' || $price_type == 'CHECK') { ?> disable<?php } ?>">
                  <div class="input-box">
                    <?php ItemForm::price_input_text(); ?>
                    <?php echo bet_simple_currency(); ?>
                  </div>
                  <div class="or"><?php _e('or', 'beta'); ?></div>
                </div>               
                <div class="selection">
                  <a href="#" data-price="0" <?php if($price_type == 'FREE') { ?>class="active"<?php } ?> title="<?php osc_esc_html(__('Item is offered for free', 'beta')); ?>"><span class="isTablet isDesktop"><?php _e('Free', 'beta'); ?></span><span class="isMobile"><?php _e('Item for free', 'beta'); ?></span></a>
                  <a href="#" data-price="" <?php if($price_type == 'CHECK') { ?>class="active"<?php } ?> title="<?php osc_esc_html(__('Based on agreement with seller', 'beta')); ?>"><span class="isTablet isDesktop"><?php _e('Deal', 'beta'); ?></span><span class="isMobile"><?php _e('Check with seller', 'beta'); ?></span></a>
                </div>
              </div>
            </div>
          <?php } ?>               
      </fieldset>
<?php } ?>

 in the item_post.php file 

The price box doesn't show up when editing an existing post, but still shows up in a new post. Where is the mistake?