My wife and I had the same debate. We priced everything out between:
stock cross bars ~ $100 (nope; don't want the arch)
thule cross bars and feet ~ $175 (preferred due to versatility and ease of removal)
yakima sky box ~ $450 (chosen against thule after recommendation from guy at REI who showed the mechanism and construction on yakima boxes is far superior for $100 less)
gobi or similar rack ~ $1000 (the end game)
I ultimately want to get a full length slim profile roof rack but the money just isn't there right now. I expect in the next year we'll get the rack so I didn't want to spend $175 on cross bars and feet that would only be used for a year.
The box also is a bit pricey for my budget. We instead decided to go with:
Amazon.com: Pro Series 63153 Rambler Hitch Cargo Carrier for 2" Receivers: Automotive
with
Amazon.com: ROLA 20174 Red Cargo Carrier Light Kit: Automotive
and
Amazon.com: Master Lock 2866DATSC Swivel Head Receiver Lock, Chrome: Automotive
I just posted a bunch of pics from our recent road trip with the setup. (
http://www.toyota-4runner.org/5th-gen-t4rs/203610-docs-roadrunner-trip-mod-thread.html#post2092962) It worked beautifully with no issues. There was only the faintest wobble, but once the rack was loaded, it was rock steady. Even packed it just right so the hatch could open and the dog could get in and out of the back with ease.
I was a bit OCD and tie wrapped (zip tied) all of the lighting cables underneath the tray. I bought a 3 foot extension cable due to my overzealous use of ties. After all is said and done, I don't think we couldn't have gotten a better outcome even with the thule feet/bars and yakima box. Everything was easily accessible with no need for climbing and hoisting bags over my head.
We brought a $12 box of assorted bungee cords and a gray tarp. The cords came in handy for reorganizing items and for tying the tarp around the luggage for the 2 brief rain showers we encountered. For offroading, we just added a 3rd tie down strap across the entire load. Everything stayed in place during a 4 hour off road adventure through Joshua Tree.
I would say if you want the gobi but can't afford it, you most likely won't be able to comfortably afford the rails and box either. This setup was all under $300 for everything. When you do get your rack, this is just another option you'll have for your pack out opposed to the bars you won't be able to use later.