DL dvd burners are dirt cheap. I got mine 2 years ago for 35 bucks after MIR. DL discs are cheap though, look on newegg, it's like 8 bucks per 3 or 5 discs. But they are affordable if you only need a couple.
your not going to be able to split the image in a way that will be usable, if you were to split the iso, you'd have to do it in multiple rars and recreate the full 7.7gb image on the machine you wanted to use it on
(but all academic as you have a dual layer burners anyway )
Blank DL Dvds are about $2 a disc
Now if you are a Smart Shopper you can find them as low as $1.20 a disc but
Now that is expensive when compared to regular dvds which go for as low as $0.15 cents a disc.
Hopefully the price will drop soon enough
Peace