Beginner : delete a line with repeating pattern

echo "house boat car, , , ," | sed '/, \{4\}$/d' this works (4 commas in a row)
How do I deal with 

echo "house boat car, , , , $"    a comma followed by a space 4 times. I tried the [ ] but it didnt work
echo "house boat car, , , ," | sed '/[, ]\{4\}$/d'
echo "house boat car, , , , " | sed '/, \{4\}$/d'

Thanks !!