I will semi-agree with the OP
sometimes people are paying for is a old tired design that hasn't had any major updated in over a decade.

But then again you also are not only paying for the RC you are also paying for customer service in case you have an issue. I read so many customer service issues with a certain low cost RC manufacturer where people have been on the phone 6 hours on a long distance calls (as they have no 1-800 number, and were disconnected multiple times) just to be told to go buy the part that came broken in the box if the phone even got answered. Where as for example I trashed an HPI RC's diffs I e-mailed HPI they sent me a new one, or with axial I got a malformed shock shaft, and told them only question they had for me was my address they didn't even ask for a pic.

Also the cheap ones share designs with multiple platforms(which usually isn't a good idea) like I know that the low end company I was talking about earlier they use a sedan chassis, for a buggy, and a monster truck they only swap out the arms, dog bones, and shocks. The monster truck version(specially the brushless one) has so many issues due to this that it shouldn't even be sold for example the arms compress too far and bend dogbones due to them just jacking it way up, and not redesigning the suspension like it should have been.

And as mad modder said the low end can be fun. Hell one of my favorites is a DF-02 which I got for $120 new I'll be honest I've probably had more fun with that than my 1/8th scales which the electronics alone cost almost 2X more than the df-02 kit did. But there is no way in hell the DF-02 I used as an example can do anything remotely near what my RCs that cost 4X more can do and come out in one piece (or probably 5 pieces at that point). Now if I'm putzing around my neighbor hood just jumping off/driving up curbs or whatnot I'll take out my lower end ones cause they server the purpose perfectly fine as well as do a great job, but if I'm going to a BMX park for example, and expect massive air or extreme stress from impacts on the RC I have to pull out my more expensive ones which can take the abuse.

Also as foxy said bargains do show up like the jammin .5 CRT kit which is sold for $75 from ofna which can be up and running for under $120 either way (electric or nitro) that can take a beating