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 (
    427920, 428694, 454298, 452982, 456262, 
    419210, 457460, 402409, 423506, 458274, 
    436405, 403215, 414680, 433452, 427170, 
    404004, 456880, 452598, 453013, 426987, 
    402780, 411115, 437229, 424420, 422451, 
    420738, 440135, 427608, 430254, 422033, 
    405045, 420628, 445650, 409275, 417856, 
    421213, 459072, 434781, 459407, 447088, 
    436478, 422140, 428560, 456487, 411199, 
    403278, 449543, 407451
  ) 
  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 0.00236

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.198563002,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_prices",
          "access_type": "range",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "key": "usergroup",
          "key_length": "9",
          "used_key_parts": ["product_id", "usergroup_id", "lower_limit"],
          "loops": 1,
          "rows": 96,
          "cost": 0.16771496,
          "filtered": 50,
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.product_id in (427920,428694,454298,452982,456262,419210,457460,402409,423506,458274,436405,403215,414680,433452,427170,404004,456880,452598,453013,426987,402780,411115,437229,424420,422451,420738,440135,427608,430254,422033,405045,420628,445650,409275,417856,421213,459072,434781,459407,447088,436478,422140,428560,456487,411199,403278,449543,407451) and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}