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 (
    51529, 51459, 51457, 51460, 51051, 51053, 
    51501, 51530, 51464, 51478, 51551, 
    51469, 51510, 51486, 51531, 51467, 
    51044, 51047, 51461, 51475, 51477, 
    51473, 51437, 51525, 51540, 51545, 
    51048, 51458, 51463, 51516, 51532, 
    51492
  ) 
  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 0.00080

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "24.21"
    },
    "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": 36,
        "rows_produced_per_join": 7,
        "filtered": "19.96",
        "index_condition": "(`test_uchur_k`.`cscart_product_prices`.`product_id` in (51529,51459,51457,51460,51051,51053,51501,51530,51464,51478,51551,51469,51510,51486,51531,51467,51044,51047,51461,51475,51477,51473,51437,51525,51540,51545,51048,51458,51463,51516,51532,51492))",
        "cost_info": {
          "read_cost": "23.49",
          "eval_cost": "0.72",
          "prefix_cost": "24.21",
          "data_read_per_join": "172"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`test_uchur_k`.`cscart_product_prices`.`lower_limit` = 1) and (`test_uchur_k`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}