...unless found with frankenparts from a dealer who discounts because of that, or found in the wild for cheap, have never been a good budget option.
I generally spend about 20 minutes on a recovered 4 (to flatten and then prepare the iron and cap iron, and tighten all of the screws).
I do recognize that i didn't spend 20 minutes on the first one. It's tempting to offer to clean up planes for people, but not tempting enough
(comments re: friction include wax - there's still a pretty big difference. When I tested irons for durability, I used a bronze LN 4 - which is stickier than cast. paraffin every 20 strokes. It's hard to keep up that kind of waxing schedule in use, but in a test, it was just part of the count).
I've learned something other people seem to have figured out before me, too - to buy planes that already look like they're in good shape with all of their parts unbroken and there. The 20 minute comment only holds when everything is there and in decent shape. I couldn't identify the last time I got a smaller stanley plane and didn't flatten it and address the cap iron, though (polishing the contact area and truing up the meeting point between cap and iron). They just work better with those two things done and just making the statement that I think those 20 minutes are worthwhile draws criticism elsewhere.
There has been but one thing I've had to fix on stanley planes Type 20 and earlier - some of the round top irons are monstrously soft, but replacement irons (new or used) are easy to find.
That said, if someone wants to buy a premium plane for no reason other than that they want to, that's plenty of reason. we should be doing things we "want" to do, rather than obligations laid over our shoulders by other people as dogma.