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 (
    6198, 6199, 6200, 6732, 2836, 2837, 2838, 
    2839, 2840, 6422, 6423, 6424, 6425, 
    2937, 2938, 2939, 2940, 2941, 6522, 
    6523, 6524, 6525, 2189, 2190, 2191, 
    2192, 2193, 2194, 2195, 2196, 2197, 
    2720, 2721, 2722, 2723, 2769, 2770, 
    2771, 2772, 2773, 2774, 2775, 2776, 
    2777, 2845, 2846, 2847, 2848, 2849, 
    2850, 2851, 2852, 2853, 2854, 2855, 
    2856, 2857, 2858, 2859, 2860, 2861, 
    2862, 2942, 2943, 2944, 2945, 2946, 
    2947, 2948, 2949, 2950, 3037, 3038, 
    3039, 3040, 3041, 3042, 3043, 3044, 
    3045, 3853, 5790, 5791, 5792, 5793, 
    5794, 5795, 5796, 5797, 5798, 6307, 
    6308, 6309, 6310, 6311, 6357
  ) 
  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 0.00170

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "67.21"
    },
    "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": 96,
        "rows_produced_per_join": 19,
        "filtered": "20.00",
        "index_condition": "(`gaseus`.`cscart_product_prices`.`product_id` in (6198,6199,6200,6732,2836,2837,2838,2839,2840,6422,6423,6424,6425,2937,2938,2939,2940,2941,6522,6523,6524,6525,2189,2190,2191,2192,2193,2194,2195,2196,2197,2720,2721,2722,2723,2769,2770,2771,2772,2773,2774,2775,2776,2777,2845,2846,2847,2848,2849,2850,2851,2852,2853,2854,2855,2856,2857,2858,2859,2860,2861,2862,2942,2943,2944,2945,2946,2947,2948,2949,2950,3037,3038,3039,3040,3041,3042,3043,3044,3045,3853,5790,5791,5792,5793,5794,5795,5796,5797,5798,6307,6308,6309,6310,6311,6357))",
        "cost_info": {
          "read_cost": "65.29",
          "eval_cost": "1.92",
          "prefix_cost": "67.21",
          "data_read_per_join": "460"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`gaseus`.`cscart_product_prices`.`lower_limit` = 1) and (`gaseus`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}