If you buy balls in Aliexpress, I highly recommend finding a guy who can give you a bulk discount on DHS D40+. Sometimes you can get 50 balls for 30€ which is like 0.6€ per ball. Most of the price is shipping so.. The more you put in a package, the more you can save. If you go around a club and ask, you can find that people will buy a box of balls if they like it.
I've purchased a box of every available balls for testing. Joola, Tibhar, Donic, Gewo, Prott, Sanwei, DHS (two kinds), Butterfly, Double Fish and XUSHAOFA. DHS D40+ won, Double Fish WTT runner up. Now everyone just once a half a year contributes to the group order. It comes to like a couple of €€€ per box, so people just acecpted it, and always carry a box. I think I lost more balls than broken.