SELECT 
  cscart_product_prices.product_id, 
  MIN(
    IF(
      cscart_product_prices.percentage_discount = 0, 
      cscart_product_prices.price, 
      cscart_product_prices.price - (
        cscart_product_prices.price * cscart_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_product_prices 
WHERE 
  cscart_product_prices.product_id IN (
    12, 162, 159, 158, 240, 238, 239, 245, 
    242, 243, 214, 217, 218, 206, 207, 198, 
    199, 136, 65, 64, 63, 66, 62, 134, 135, 
    205, 129, 127, 131, 121, 103, 33, 32, 
    182, 246, 208, 229, 211, 210, 209, 71, 
    70, 69, 68, 67, 215, 226, 213
  ) 
  AND cscart_product_prices.lower_limit = 1 
  AND cscart_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  cscart_product_prices.product_id

Query time 0.00098

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_product_prices.product_id",
      "temporary_table": {
        "table": {
          "table_name": "cscart_product_prices",
          "access_type": "ALL",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "rows": 253,
          "filtered": 13.99961281,
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.product_id in (12,162,159,158,240,238,239,245,242,243,214,217,218,206,207,198,199,136,65,64,63,66,62,134,135,205,129,127,131,121,103,33,32,182,246,208,229,211,210,209,71,70,69,68,67,215,226,213) and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    }
  }
}