Economic inflation is a complex phenomenon that boils down to basic human instincts reacting to change. Prices go up, in other words. Runaway Number Inflation is similar, but not. It's like... okay, the title doesn't make technical sense, but...
Runaway Number Inflation is when the values on cards skyrocket into progressively larger and eventually sillier numbers. This mostly affects Point Cards, but is by no means limited to that. Attack Values, Resources, whatever; it's easy enough to just make the number higher than everything else. This has the unfortunate effect of devaluing earlier cards and reducing the already leaky gameplay into "who can write the most stupidly high number." The 1000 Point Limit is a good way of curtailing this, but a solution that solves the cause instead of just the effect is to make the players quit being so competitive. If you don't do that, the 1000 Point Limit is a good way to get a bunch of +/- 1000 Points cards.
An alternative to the 1000 Point Limit is a Scaling Point Limit, which has a ceiling that increases based on earlier cards. Another alternative is a rule that says a card may not take or give more than 1000 points without any conditions attached.
What's interesting is that this effect is evident even in commercial card games (the ones that add new cards, anyway). An easy way to get the newer cards to be desirable is to make them more powerful for less cost. This is still a bad thing, by the way; how would you like to know that your card investment is suddenly worthless? Magic: The Gathering has largely avoided this (its Attack/Defense values have no limit but rarely exceed 10/10), but games like Pokemon and Yu-gi-Oh! have succumbed.
There is another side to this effect. Larger numbers seem more powerful, even if the relative discrepancy between the weakest and strongest cards is the same. Notice: Magic has numbers starting in the ones digits. Pokemon appends a 0 to all of its numbers. Cards have to be at least a 1000 in Yu-gi-Oh! to be decent. And Duel Monsters regularly goes into the ten thousands. The problem is, the human capacity for quickly recognizing numbers rapidly disintegrates around the five-digit mark, especially without distinguishing marks like commas. For the sake of expediency, use small numbers.