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 (
    6778, 6793, 7698, 8960, 9014, 10148, 
    10325, 10420, 10128, 6494, 6575, 6579, 
    6674, 6718, 6816, 7540, 7543, 10122, 
    10217, 6496, 6548, 6775, 6809, 10387, 
    6715, 6758, 6766, 6768, 6717, 6771, 
    6813, 6716, 6772, 6669, 6671, 6812, 
    7522, 6761, 6672, 7516, 11046, 11255, 
    11277, 10428, 6760, 7699, 10956, 11067, 
    10312, 10453, 6767, 6815, 7704, 7729, 
    10226, 10471, 10196, 7751, 10219, 10365, 
    10398, 10463, 11280, 6759, 10315, 7753, 
    6668, 6762, 6765, 6810, 7750, 10406, 
    10436, 10480, 10486, 10545, 11155, 
    11456, 6404, 6757
  ) 
  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 0.00202

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "88.41"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "product_id",
        "used_key_parts": [
          "product_id"
        ],
        "key_length": "3",
        "rows_examined_per_scan": 152,
        "rows_produced_per_join": 30,
        "filtered": "19.99",
        "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`product_id` in (6778,6793,7698,8960,9014,10148,10325,10420,10128,6494,6575,6579,6674,6718,6816,7540,7543,10122,10217,6496,6548,6775,6809,10387,6715,6758,6766,6768,6717,6771,6813,6716,6772,6669,6671,6812,7522,6761,6672,7516,11046,11255,11277,10428,6760,7699,10956,11067,10312,10453,6767,6815,7704,7729,10226,10471,10196,7751,10219,10365,10398,10463,11280,6759,10315,7753,6668,6762,6765,6810,7750,10406,10436,10480,10486,10545,11155,11456,6404,6757))",
        "cost_info": {
          "read_cost": "85.37",
          "eval_cost": "3.04",
          "prefix_cost": "88.41",
          "data_read_per_join": "729"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`lower_limit` = 1) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}