Re: fencing
I don't know how often this occurs, but fencing equipment standards change, requiring new purchases, and changes in allowable and practical technique.
I fenced a little, using foil, up to about 1980. About 15 or 20 years later, I went to a local club session, and brought my old equipment - I couldn't use it. And not just for competitions, because it wasn't electric.
Apparently "foils" became completely different - much stiffer, almost like Épées used to be. I think some decided the old ones were unsafe, because they were too flexible and fragile - i.e., the tip could break off, leaving a sharp point. That must also radically change the technique, because I guess you can no longer whip the point into place, and perhaps the stiffer and heavier blades alter circular parries. I wouldn't be surprised if old jackets weren't thick enough to provide sufficient protection against the newer style blades.
Also, the person in charge wouldn't let me use what used to be one of my favorite moves, on the basis of safety, where you go into a deep lunge. She claimed it wasn't safe to bend the knee past 90 degrees (like, of course, everyone does in figure skating). I'm not sure if that was an actual rule, or just what she had been taught. Also, for some reason, the moves in which you pass or come side-by-side with someone, then touch their back from behind, were apparently banned, or maybe are just impractical with electric equipment.
Even when I fenced, the altered scoring system, and the use of electric equipment in tournament play had forced people to move along narrow lanes, radically changing the nature of fencing (and dueling) styles of a few decades earlier, when people danced and circled around each other.
Perhaps older styles of equipment and technique are still used by the Society for Creative Anachronisms (SCA), Markland, and the Renaissance Fair people - or by some of the martial arts fans...
It would not be at all surprising if wireless fencing equipment will soon completely replace the current generation of equipment, again requiring new purchases, and changes in allowable and practical technique - including, perhaps, a partial return to older techniques. So you may soon need to buy more stuff, and get new lessons.
And maybe you now need to augment your training with WII and other video games, adding another dimension to cost.
In contrast, figure skates and clothing styles change, but you can still theoretically skate with old style skate equipment and clothing, even for tests and competitions - I think.
BTW, some college and university fencing clubs admit older folk - and probably charge a lot less.