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 (
    12748, 15130, 2282, 2723, 15152, 15153, 
    2725, 2728, 2732, 2729, 2722, 15126, 
    2828, 2714, 2715, 2716, 2717, 2713, 
    2623, 2622, 15128, 2724, 2726, 2727, 
    2730, 15151, 15150, 15423, 3216, 2718
  ) 
  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 0.00775

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": "ref",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "key": "lower_limit",
          "key_length": "3",
          "used_key_parts": ["lower_limit"],
          "ref": ["const"],
          "rows": 6449,
          "filtered": 7.156754494,
          "attached_condition": "cscart_product_prices.lower_limit <=> 1 and cscart_product_prices.product_id in (12748,15130,2282,2723,15152,15153,2725,2728,2732,2729,2722,15126,2828,2714,2715,2716,2717,2713,2623,2622,15128,2724,2726,2727,2730,15151,15150,15423,3216,2718) and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    }
  }
}