It's a reasonable price for the roll of pipe plus the unions, but you'll still need a length of steel pipe or maybe Kunifer, to do the bits across the back axle. Copper, unless you make a couple of coils to allow for the movement, is not ideal for any application where the cylinders move relative to the backplates. Automec kits do not include enough pipe to allow for the coils, other brands of pre-cut sets may be the same that way. That roll is at least enough to make a couple of replacements the first couple of times the pipes fracture.
Someone, I think it may well have been Ian (Sprint95m), suggested that flexible hoses could be utilised from the ends of the rear axle pipes to the cylinders, an idea that I happen to consider ideal if short pipes (Peugeot 405 rears?) can be sourced or made, but copper work-hardens too quickly for this job and I've seen a few that have failed for that reason, on vehicles using the same rear brake arrangement. (Rebels, Scimitars, etc.)
Yes, this is a pet concern of mine, but I don't think that there's any excuse to risk brake failure for the want of a correct material for the pipes. The failures I've encountered have mostly been on dual-purpose, road/track cars, only one on a pure road car, in all cases, the copper pipes that let go had only been in place for around 10,000 miles. OK, for some that will be more than the 6 Months of use that it represents for me, but why take the risk?