Yup I built an electric skateboard but ended up being like $700 or so even going "cheap" so not sure what to tell ya on the pricing there. Problem is the best esc for this kind of higher voltage stuff is arguably either the VESC or the o-drive, both are pretty pricey because the MOSFETs used need to be able to handle the voltage and current and are themselves like $6 a pop at least and need 6 of them plus other components and assembly so it all adds up even though the software is open source and free (even open hardware designs that can be copied but the components are just pricey). Beyond that the battery ends up costing a lot no matter what basically, I have one deck with 185Wh of lipo from hobby king on it and was around $100 for that pretty short range setup (use about 10Wh per mile if efficient setup and light rider, 20Wh per mile it using pneumatics tires or larger rider). My second build is pneumatic and has big ol battery in it but was like $300 for the battery itself (10S 5P from metroboards 485Wh I think)
There are cheapo ESCs that can kinda do the job but aren't nearly as configurable for various power input or controlling speed ramping or reading temp sensors and using HFI or other means of rotation sensing to avoid motor cogging at low speeds and other issues.