the FX8 was designed for using with a guitar amp and there are much higher-end components in it to keep noise at a minimum. the first product of its kind from FAS for this specific purpose, as opposed to making an amp modeler also work for that purpose. if that's the price for the FX8 and its components, that's the price. what we do know is that it will continue to be updated and improved over time, which helps it keep its value.
i'm successfully using an FX8 at "general" gigs going direct, using a Fender Micro DI pedal that is an amp/cab simulator (no options, just a amp sim). but i really do miss the amp/tone options found with Amp modeling. having the FAS quality in such a small unit like the FX8 is amazing, but i'm definitely a fan of modeling and haven't touched a real amp in years.
i don't think the AX8 has "more for only $50." i think it has a different usage, which happens to be $50 more. it's been very difficult to explain to "Amp Guys" how to interface an Axe-Fx II with their real amp setups - having to take out the Amp/Cab blocks from every factory preset and explain why sometimes is very confusing. the FX8 is definitely easier to setup with a real amp, i feel.
also, as we've seen, the progress made on the AX8 might/should be heading over to the FX8, like being able to freely assign switches per preset, etc. so we don't really know what the immediate future holds for the FX8 and updates. but it's a great product and its price is on par with building a high-end pedal board of individual components.
different products for different uses. it's a great time to be a guitarist!