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 (
    94742, 94741, 94740, 94739, 94738, 94737, 
    94736, 94735, 94734, 94733, 94732, 
    94731, 94730, 94729, 94728, 94727, 
    95619, 95618, 95617, 95616, 95615, 
    95614, 95613, 95612, 95611, 95610, 
    95609, 95608, 95607, 95606, 95605, 
    95604, 95603, 95602, 95601, 95600, 
    95599, 95598, 95597, 95596
  ) 
  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 0.00085

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_product_prices range usergroup,product_id,lower_limit,usergroup_id usergroup 9 80 Using where

Result

product_id price
94727 1.69000000
94728 1.69000000
94729 1.69000000
94730 1.69000000
94731 1.69000000
94732 1.69000000
94733 1.69000000
94734 1.69000000
94735 1.69000000
94736 1.69000000
94737 1.69000000
94738 1.69000000
94739 1.69000000
94740 1.69000000
94741 1.69000000
94742 1.69000000
95596 1.69000000
95597 1.69000000
95598 1.69000000
95599 1.69000000
95600 1.69000000
95601 1.69000000
95602 1.69000000
95603 1.69000000
95604 1.69000000
95605 1.69000000
95606 1.69000000
95607 1.69000000
95608 1.69000000
95609 1.69000000
95610 1.69000000
95611 1.69000000
95612 1.69000000
95613 1.69000000
95614 1.69000000
95615 1.69000000
95616 1.69000000
95617 1.69000000
95618 1.69000000
95619 1.69000000