Price it out, you might be able to get a cheaper made cable from a company like CDW. You could also have a local computer/networking store create one for you.
Cat5e can handle weather conditions, especially in your attic. Generally, if you don't have access to the cable and it is through a wall or not in the open, you will need to use plenum. That would be to code but since it is only a single cable, I would save the money and use a regular cable. The poisonous gas emitted when burning is only dangerous if you have a lot of it burning and you're inhaling a lot of it. Based on that one cable, the smoke will get you first if you decided to stay in your house.
lowes and home depot in my area also sell 100ft+ at good prices.. even cat6 and 7 and one that claims to be ultra?? or x2 the bandwidth of previous versions. if the hardware you use supports such things.
btw, each patch in to a wire, causes more resistance and lag..noticable in ping tests... it's best to get one complete wire to the router and the pc.. without switches, patches or tap ins..
If possible further performance can be had if you can position the router where you wouldn't need more then 12-30ft... the more copper you have to run through, the higher the ping times will be inside and outside the home network..
maybe 1-10ms per 30ft. possibly not even a blip on the screen, noticable..
but for HD video and gameing this adds to ping that is already there. And is often very noticeable. it could be less ping with diffrent types of cables...cat5 vs cat 6 etc.. cheap wire vs more expensive 100% pure copper with gold plated connections..silver is actually a better conductor etc etc..