I may be wrong, never having really owned a more expensive gun, but the more expensive ones likely do what the cheaper ones do after a tune. So, if you say a $150 gun, and you get a $150 tune, that's already a $300 gun. A tune hones the action and replaces parts that are inferior. But that only brings you part way. Then there are special features. Like cars...if you are just getting to and from work you don't want an indy racer. Lots of people like to 'work on' cars...customize, and personalize. More expensive guns might have features to reduce kick (opposing springs), additional trigger stages, barrel and sight differences and convenience features. Better rails and stops.
Getting what I get out of my cheaper-guns-with-a-tune, I don't see how I can justify a gun in the 600-1000 range, especially for backyard fun. Above that in the Indy Racer category I have no business. I am currently putting together a rifle for that price range, but it is custom, starting with a damaged stock TF89 and a tune. I'll be getting a custom stock, custom muzzle brake, and in the end will have a unique gun. My bet is I get great accuracy better feel, and pride of ownership (stock and brake designs will be my own). It will likely be the most I'll ever spend on a rifle. The trigger will be good, the power will be good, the accuracy will be good. it'll be fun to shoot.
I think the cheap guns got a bad rap when they were cheap and poorly manufactured. Now they have some quirks, but seems like those quirks can be worked out for significant savings and a lot of fun!
There's my ignorant take on it.