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 (
    13018, 13017, 13016, 13015, 13014, 13013, 
    13012, 13011, 13010, 13009, 13008, 
    13007, 13006, 13005, 13004, 13003, 
    13002, 13001, 13000, 12999, 10812, 
    10811, 10810, 10809, 10808, 10807, 
    10806, 10805, 10804, 10803, 10802, 
    10801
  ) 
  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 0.00469

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_prices",
      "access_type": "range",
      "possible_keys": ["usergroup", "product_id", "lower_limit", "usergroup_id"],
      "key": "product_id",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 32,
      "filtered": 99.23484039,
      "index_condition": "cscart_product_prices.product_id in (13018,13017,13016,13015,13014,13013,13012,13011,13010,13009,13008,13007,13006,13005,13004,13003,13002,13001,13000,12999,10812,10811,10810,10809,10808,10807,10806,10805,10804,10803,10802,10801)",
      "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
    }
  }
}

Result

product_id price
10801 1582.30000000
10802 1582.30000000
10803 1582.30000000
10804 1582.30000000
10805 1582.30000000
10806 1582.30000000
10807 1582.30000000
10808 1582.30000000
10809 1582.30000000
10810 1582.30000000
10811 1582.30000000
10812 1582.30000000
12999 2061.44000000
13000 2061.44000000
13001 2061.44000000
13002 2061.44000000
13003 2061.44000000
13004 2061.44000000
13005 2061.44000000
13006 2061.44000000
13007 2061.44000000
13008 2061.44000000
13009 2061.44000000
13010 2061.44000000
13011 2061.44000000
13012 2061.44000000
13013 1927.73000000
13014 1927.73000000
13015 1927.73000000
13016 1927.73000000
13017 1927.73000000
13018 1927.73000000