Vending taxes is just another form of zeny sink and a really good one. Now on kRO, they start charging taxes at the 10m threshold, items below this price, will be exempt of taxation.
Now of course, it will not be worth it selling expensive items using Vending and it will be a hassle go into Eden and create a chat as an alternative for this but, there's a better alternative to promote your items and even gives you the possibility to do more things with it and it's, implementing the megaphone. This is what people do in kRO when they want to sell something expensive and is also commonly used to promote parties and such. This item could even solve the issue that we have on Eden right now, people all clumped up in the lobby, since this is the only place to really communicate to other players. Using Eden is not a bad place to socialize with people but, it will feel more liberated if there could be other options to communicate as well. Cities will feel more organic and alive since players will not have the need to be always on Eden to search for parties or to buy items.
The megaphone is a daily reward on kRO. I don't know if it can be obtainable via cash shop or zeny but, all of this options are good ways to have it available, cash for profit, zeny for zeny sink and daily reward to entice people to play the game. This also can be implemented as a VIP feature like the daily Token of Siegfried.
I would log in Thor again during WoE just to read the megaphone broadcasts.