Cheapest priced copy (The Lord of the Rings: Tales of Middle-earth): $0.35 at Card Kingdom, near mint, their price list as of .
Bag End Porter 
Creature — Dwarf · 4/4 · Common · The Lord of the Rings: Tales of Middle-earth · #153
Whenever this creature attacks, it gets +X/+X until end of turn, where X is the number of legendary creatures you control.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Lord of the Rings: Tales of Middle-earth | 153 | Common | $0.35 | $0.49 |
| The Lord of the Rings: Tales of Middle-earth | 604 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 16 June 2023The value of X is determined only as Bag End Porter's triggered ability resolves. It won't change later in the turn if the number of legendary creatures you control changes.