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 (
    3618, 4080, 4081, 4082, 4083, 4084, 4085, 
    4086, 4156, 4157, 4158, 4159, 4160, 
    4161, 4162, 4209, 4210, 4211, 4212, 
    4213, 4214, 4215, 3102, 3110, 6670, 
    6685, 6698, 3095, 3101, 3108, 6683, 
    6697, 3099, 19, 20, 21, 3929, 3930, 3931, 
    6724, 3100, 3106, 3114, 3120, 3125, 
    3153, 3154, 6672, 6688, 6689, 6694, 
    6702, 6706, 6708, 6726, 6725, 3103, 
    3097, 3113, 6687, 6699, 36, 37, 38, 39, 
    40, 41, 42, 83, 84, 85, 86, 87, 88, 89, 
    147, 148, 149, 150, 151, 152, 153, 168, 
    169, 170, 171, 172, 173, 174, 250, 251, 
    252, 253, 254, 255, 256
  ) 
  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 0.00162

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 (3618,4080,4081,4082,4083,4084,4085,4086,4156,4157,4158,4159,4160,4161,4162,4209,4210,4211,4212,4213,4214,4215,3102,3110,6670,6685,6698,3095,3101,3108,6683,6697,3099,19,20,21,3929,3930,3931,6724,3100,3106,3114,3120,3125,3153,3154,6672,6688,6689,6694,6702,6706,6708,6726,6725,3103,3097,3113,6687,6699,36,37,38,39,40,41,42,83,84,85,86,87,88,89,147,148,149,150,151,152,153,168,169,170,171,172,173,174,250,251,252,253,254,255,256))",
        "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)))"
      }
    }
  }
}