I have not done a side by side comparison of a bought screen and a DIY but everything I have read is that a well made DIY screen is not put to shame by a purchased screen as long as cost is a factor. I made my screen for a total cost of about 130 € and am very impressed with the end result.
I used Tikkurilla Harmony X073, it seems to be a very popular paint to use here in Finland, it is painted onto a sheet of MDF with a black frame around the edges. Easy to make even for someone like me who has never been great at woodwork with pleasing results, also satisfying to know that it is DIY.