I don't believe MapleStory was intended to be played with 100 online players. A lot of items do not go on the market due to low population and some players (cough archers) end up skipping weapon tiers because nobody is selling them.
Some solutions I thought about:
Upgrade stones
Lv50 Weapon Upgrade Stone
Upgrades a Lv40 weapon to a Lv50 weapon with random stats. (might be easier to just make an exchange NPC for this though) Drops from all lv50-59 mobs at a low chance comparable to scrolls. Tradeable. These tokens will go up to lv70.
Secret merchants
Every hour, there will be a small chance that a player shop will appear in FM with a few lv50-lv70 weapons for an affordable price (could spice this up with some random scrolls and minigame materials too!). Location is random so people actually have to search the FM maps.
Some solutions I thought about:
Upgrade stones
Lv50 Weapon Upgrade Stone
Upgrades a Lv40 weapon to a Lv50 weapon with random stats. (might be easier to just make an exchange NPC for this though) Drops from all lv50-59 mobs at a low chance comparable to scrolls. Tradeable. These tokens will go up to lv70.
Secret merchants
Every hour, there will be a small chance that a player shop will appear in FM with a few lv50-lv70 weapons for an affordable price (could spice this up with some random scrolls and minigame materials too!). Location is random so people actually have to search the FM maps.