SELECT 
  vi_product_prices.product_id, 
  MIN(
    IF(
      vi_product_prices.percentage_discount = 0, 
      vi_product_prices.price, 
      vi_product_prices.price - (
        vi_product_prices.price * vi_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  vi_product_prices 
WHERE 
  vi_product_prices.product_id IN (
    187, 232, 230, 231, 170, 131, 177, 186, 
    185, 179, 233, 152, 160, 237, 235, 122, 
    115, 129, 127, 188
  ) 
  AND vi_product_prices.lower_limit = 1 
  AND vi_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  vi_product_prices.product_id

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "vi_product_prices.product_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "vi_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": 255,
              "filtered": 100,
              "attached_condition": "vi_product_prices.lower_limit <=> 1 and vi_product_prices.product_id in (187,232,230,231,170,131,177,186,185,179,233,152,160,237,235,122,115,129,127,188) and vi_product_prices.usergroup_id in (0,1)"
            }
          }
        ]
      }
    }
  }
}