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 (
    73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 
    84, 85, 91, 90, 86, 87, 88, 92, 89, 99, 
    95, 96, 97, 98, 93, 94
  ) 
  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 0.00142

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.043281977,
    "filesort": {
      "sort_key": "cscart_product_prices.product_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_product_prices",
              "access_type": "ALL",
              "possible_keys": [
                "usergroup",
                "product_id",
                "lower_limit",
                "usergroup_id"
              ],
              "loops": 1,
              "rows": 102,
              "cost": 0.02598891,
              "filtered": 26.47058868,
              "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.product_id in (73,74,75,76,77,78,79,80,81,82,83,84,85,91,90,86,87,88,92,89,99,95,96,97,98,93,94) and cscart_product_prices.usergroup_id in (0,1)"
            }
          }
        ]
      }
    }
  }
}