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 (
    195, 199, 198, 94, 96, 201, 192, 136, 191, 
    90, 196, 252, 95, 197, 251, 200, 84, 85, 
    88, 47, 253, 138, 93, 87, 139, 83, 204, 
    256, 137, 248, 108, 97, 121, 286, 103, 
    89, 110, 82, 100, 194, 202, 203, 111, 
    104, 123, 118, 119, 112, 114, 116
  ) 
  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 0.00139

JSON explain

{
  "query_block": {
    "select_id": 1,
    "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"
              ],
              "rows": 264,
              "filtered": 15.39423561,
              "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.product_id in (195,199,198,94,96,201,192,136,191,90,196,252,95,197,251,200,84,85,88,47,253,138,93,87,139,83,204,256,137,248,108,97,121,286,103,89,110,82,100,194,202,203,111,104,123,118,119,112,114,116) and cscart_product_prices.usergroup_id in (0,1)"
            }
          }
        ]
      }
    }
  }
}