I thought the same thing until I started pricing things out... I couldn't find a good enough price difference to justify it, unless you can find a good used set of Deavers.
Artec industries, and others, have kits. Everything you need for $1100.
Artec Industries Easy 3 Link - Kit G - Adjustable Upper link
Rear 3-link is easy since you will be welding lower mounts to bottom of frame like they are stock, and the upper goes inside the frame rail behind the transfer case. Deavers will run you $800+ and then you need mounts and shackles still. Unless you make your own you're still looking at $1k. You'd only save money on the shocks vs coilovers/shock & coils.
Coils, shocks, coilovers would be the money part depending on what you want to run. Personally I plan on coilovers in the back too for simplicity, more specifically for myself I want to use ORI-STX-STRUTS. They are more expensive, but no worrying about buying different coils trying to get spring rates right, it's all nitrogen charged and oil filled to specific CC levels to achieve desired spring rates.
The biggest issue with long travel in the rear is shock length though. To long and you'll be mounting them inside, not long enough and you aren't really long travel, or custom sideways mount talking big money. (forget what it's called) I was thinking cutting a hole in the fenderwell, making a mount that goes inside, then making a sheet metal box to put over it. Spray thick bedliner inside to reduce noise, cover outside of box in sound deadening material and cover with carpet or whatever to achieve desired look. For plastic inside, either cut a hole that the metal box fits through, or go all out and make a sheet metal panel to replace plastic ones, repeat bedliner and sound deadening to keep noise levels down while mobbing through the dirt!
Didn't mean to clog this thread up.... You need to make a bold thread! Or even a long travel talk thread! Then we can bounce idea's and let others chime in with (hopeful) advice. And ya, I know you've probably already thought of all this too! Lol I'm just thinking out loud.
Sent from the drivers seat of my 05 4runner.