The latest Proton can get payload to orbit for a lower price per kg than an expendable Falcon 9. The price difference isn't huge, less than 10%, and it comes at the cost of using UDMH/NTO for its propellant. This propellant combination is both highly explosive and highly toxic. It's an acceptable propellant choice for ICBMs, which the Proton was developed as, but for everything else it's really unacceptable. The price of the Proton also does not include development costs, making every flight in essence subsidized by the Russian government. Once the price of the Falcon 9 drops due to reusability, it will be the cheapest launch vehicle per kg of payload.