You need to try this code.When we create
 new selection field on the prin_format you must add new functions for 
that types and need to create new printing format
| from collections import defaultdictfrom odoo import fields, models, _
 from odoo.exceptions import UserError
 
 
 class ProductLabelLayout(models.TransientModel):
 _inherit = 'product.label.layout'
 
 print_format = fields.Selection(selection_add=[
 ('price_card', 'Price Card'), ], ondelete={'price_card': 'set default'})
 
 def _prepare_report_data(self):
 xml_id, data = super()._prepare_report_data()
 
 if 'price_card' in self.print_format:
 xml_id = module_name.report_product_label_product_price_tag'
 
 active_model = ''
 if self.product_tmpl_ids:
 products = self.product_tmpl_ids.ids
 active_model = 'product.template'
 elif self.product_ids:
 products = self.product_ids.ids
 active_model = 'product.product'
 price = format(self.product_tmpl_ids.list_price, ".2f")
 data = {
 'active_model': active_model,
 'product_tmpl_name': self.product_tmpl_ids.name,
 'product_tmpl_price': price,
 'product_tmpl': self.product_tmpl_ids,
 'product_name': self.product_ids.name,
 'product_id': self.product_ids,
 }
 return xml_id, data
 
 def process(self):
 action = super(ProductLabelLayout, self).process()
 self.ensure_one()
 xml_id, data = self._prepare_report_data()
 if not xml_id:
 raise UserError(_('Unable to find report template for %s format', self.print_format))
 report_action = self.env.ref(xml_id).report_action(None, data=data)
 report_action.update({'close_on_report_download': True})
 return action
 | 
Also, try to add the paper format and further details
<record id="paperformat_product_price_
tag" model="report.paperformat">
    <field name="name">Price Card Label</field>
    <field name="default" eval="True"/>
    <field name="format">custom</field>
    <field name="page_height">267</field>
    <field name="page_width">175</field>
    <field name="orientation">Landscape</field>
    <field name="margin_top">0</field>
    <field name="margin_bottom">0</field>
    <field name="margin_left">0</field>
    <field name="margin_right">0</field>
    <field name="disable_shrinking" eval="True"/>
    <field name="header_line" eval="False"/>
    <field name="header_spacing">0</field>
    <field name="dpi">96</field>
</record>
<record id="report_product_label_product_price_tag" model="ir.actions.report">
    <field name="name">Product Price Card</field>
    <field name="model">product.template</field>
    <field name="report_type">qweb-pdf</field>
    <field name="report_name">module_name.report_product_price_tag</field>
    <field name="report_file">module_name.report_product_price_tag</field>
    <field name="binding_type">report</field>
    <field name="binding_model_id" ref="model_product_template"/>
    <field name="paperformat_id" ref="paperformat_product_price_tag"/>
</record>
<template id="report_product_price_tag">
    //content
</template>
Hope it helps