The most affordable manifold by far is the log manifold. Log manifolds are used in factory applications, as they’re a very simple design and can be cast, to keep costs down, but if fabricated they’re simply cheaper because less materials are used. As well as being easy and affordable to manufacture, they are extremely compact compared to a tubular manifold, which is desirable in some applications. However, log manifolds are the worst-performing design in the market, so if you’re after big power this isn’t the way to go. They don’t factor in different runner lengths, and all the exhaust gases run into a common chamber, so exhaust pulses collide and cause a huge drop in performance.
Short runner length also makes for more heat thanks to the smaller surface area, so heat doesn’t have as much chance to dissipate, and that can cause cracking and damage. Such a restrictive design means these manifolds are only suitable for low pressure and near stock applications.