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 (
    881, 894, 882, 895, 893, 950, 957, 949, 
    956, 953, 954, 951, 952, 958, 1090, 955, 
    335, 334, 156, 336, 961, 965, 963, 964, 
    962, 966, 219, 270, 1302, 272, 273, 274, 
    973, 223, 222, 160, 194, 164, 174, 158, 
    183, 192, 188, 163, 172, 184, 173, 191
  ) 
  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 0.00177

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": 48,
      "filtered": 9.795915604,
      "index_condition": "cscart_product_prices.product_id in (881,894,882,895,893,950,957,949,956,953,954,951,952,958,1090,955,335,334,156,336,961,965,963,964,962,966,219,270,1302,272,273,274,973,223,222,160,194,164,174,158,183,192,188,163,172,184,173,191)",
      "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
    }
  }
}

Result

product_id price
156 0.00000000
158 0.00000000
160 18000.00000000
163 18000.00000000
164 18000.00000000
172 0.00000000
173 0.00000000
174 0.00000000
183 0.00000000
184 0.00000000
188 0.00000000
191 0.00000000
192 0.00000000
194 0.00000000
219 0.00000000
222 0.00000000
223 0.00000000
270 0.00000000
272 0.00000000
273 0.00000000
274 0.00000000
334 0.00000000
335 0.00000000
336 0.00000000
881 0.00000000
882 0.00000000
893 0.00000000
894 0.00000000
895 0.00000000
949 0.00000000
950 0.00000000
951 0.00000000
952 0.00000000
953 0.00000000
954 0.00000000
955 0.00000000
956 0.00000000
957 0.00000000
958 0.00000000
961 0.00000000
962 0.00000000
963 0.00000000
964 0.00000000
965 0.00000000
966 0.00000000
973 0.00000000
1090 0.00000000
1302 0.00000000