video wall or bust...... to buy very expensive, to rent still very expensive. The more detail you want the more expensive it becomes. Outdoor in 6mm - 10mm will cost about $100 per square ft to rent with rigging and labor!!!! If you want 3mm - 4mm add some more $$$
It's typical for standard size LED walls to go for around $10k to rent after labor and rigging is factored in. A standard size wall is roughly 9' X 16" or 144 sq. ft. This is typical for 4-6mm LED walls. As you start getting to 4mm and below the price starts going up DRASTICALLY. Newer 1.5-2mm walls are selling new for close to 5K per panel ( 1.5sq. ft. ). You can imagine the cost of rental also goes up with it.
You need to know your audience distance. Most walls are rated for optimal viewing distance, or basically the distance in which the pixels are no longer viewable and you can see the whole panel as being one image. For sub 2mm walls this distance is roughly 10-15' whereas 4mm-10mm walls require as much 30-90' or so.