I used to do that once a month off of ebay (or off of here). See a ball, buy it just to see what it does, then sell it again a month or 2 later after it didnt work for me. If I find a ball that works well, I hang onto it for a bit, but eventually it goes away (like all my other balls do in time).
Laner
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Hell hath no fury like a woman scorn for Sega....