[RPG] Abusing Enchant Magic Item

On the gamemastering page you linked to there are guidelines on what players should spend their starting wealth on.

Table: Character Wealth by Level can also be used to budget gear for characters starting above 1st level, such as a new character created to replace a dead one. Characters should spend no more than half their total wealth on any single item. For a balanced approach, PCs that are built after 1st level should spend no more than 25% of their wealth on weapons, 25% on armor and protective devices, 25% on other magic items, 15% on disposable items like potions, scrolls, and wands, and 10% on ordinary gear and coins. Different character types might spend their wealth differently than these percentages suggest; for example, arcane casters might spend very little on weapons but a great deal more on other magic items and disposable items.

Yes, of course, removing a problematic element from the game is one of the reasons to have a DM in the first place.

But I have a hard time seeing how rod of force is that item. They’re extremely expensive (worth almost everything an 11th-level character owns, and not being realistically affordable until 15th or 16th level—and that’s just for one!), can only be used five times per day, and it functions as either a mediocre weapon, a mediocre blast attack, or wall of force, which is almost-certainly the best way to use it but I have hard time seeing how that could ruin a game. They’re fairly decent I suppose, with that flexibility, but I just don’t see how they end up being game-breaking.

For rod of force to cause so much trouble, I have to imagine that this character has vastly more wealth than the books would otherwise suggest. With that much wealth, they could be getting far more dangerous things than the rod of force. I suggest your review the wealth by level guidelines in the Dungeon Master’s Guide, unless you’re playing in the 15th+ level range—at which point, I would suggest your encounters need to be tougher if the rod of force is causing considerable problems for the players’ encounters. On a personal note, I generally feel that the game breaks apart on its own somewhere around 15th level, without any need for particular player shenanigans. I would thus suggest avoiding games that go so high, the system doesn’t work well when you do.