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 (
    10301, 10313, 10318, 10294, 10297, 10302, 
    10314, 10319, 12552, 12554, 10295, 
    10298, 10303, 10315, 10320, 10299, 
    10304, 10316, 10321, 10300, 10317, 
    10322, 12572, 12575, 12571, 12573, 
    10273, 10272, 10271, 10270, 10269, 
    10268
  ) 
  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 0.00128

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 (10301,10313,10318,10294,10297,10302,10314,10319,12552,12554,10295,10298,10303,10315,10320,10299,10304,10316,10321,10300,10317,10322,12572,12575,12571,12573,10273,10272,10271,10270,10269,10268)",
      "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
    }
  }
}

Result

product_id price
10268 2150.58000000
10269 2150.58000000
10270 2150.58000000
10271 2150.58000000
10272 2150.58000000
10273 2150.58000000
10294 2206.30000000
10295 2206.30000000
10297 3409.73000000
10298 3409.73000000
10299 3409.73000000
10300 3409.73000000
10301 4579.74000000
10302 4579.74000000
10303 4579.74000000
10304 4579.74000000
10313 2930.59000000
10314 2930.59000000
10315 2930.59000000
10316 2930.59000000
10317 2930.59000000
10318 2930.59000000
10319 2930.59000000
10320 2930.59000000
10321 2930.59000000
10322 2930.59000000
12552 14984.00000000
12554 19331.00000000
12571 67629.15000000
12572 42208.28000000
12573 68108.92000000
12575 47964.00000000