I tried to reply to this thread last night, but lost over an hour's worth of work when I hit the wrong key.

:-D:-D I'll try again, with the "condensed" version.
One of the shortcomings, in my opinion, of these "semi-craftsman-type" kits from Intermountain, Branchline, and Proto2000 is the plastic grabirons, which are frustrating to install, and are still oversize. They're also less durable than either metal ones or the cast-on variety. While some older models have heavy cast-on details, many newer cars, such as are available from Accurail or Bowser, have very finely scaled details cast in place, that, when properly weathered, look great.
You can upgrade many cheaper models to present day standards if you're willing to do the work. Actually, not just willing, but perhaps you should enjoy doing this kind of work, especially if you have any great amount of such cars to do. :-D
Other than hoppers and covered hoppers, I like to add wire grabirons to my models (I'd like to do the hoppers and covered hoppers, too, but with over 60 of them, I've been deferring this task).

Of course, you can also replace the doors and doortracks, add metal sill steps, thin-down oversize roofwalks, and add more detailed brake gear, too.
Here are some cheap (and some not-so-cheap) cars that I've modified to look, hopefully, a bit better. Many are from the "used" table at the LHS.
Athearn boxcar - $4.00, plus about $4.00 for Tichy ends, A-Line drop steps, and some Tichy grabs. The doors, and brakegear are from the scrap box, and another $2.00 for lettering from C-D-S
Train Miniature boxcar - $4.00, plus four A-Line drop steps, some wire for grabirons, and decals from MicroScale - these will do several cars, so the cost-per-car is only about a buck.
Another Train Miniature car - $4.00, plus another $10.00 or so for new doors and ends from Tichy, and grabirons, drop steps, and lettering. This is a good representation of the prototype car, for less than half what you'd pay for the resin kit from Westerfield.
Accurail USRA doublesheathed boxcar - notwithstanding my earlier comments about their finely-done grabirons, I usually replace the side grabs with metal parts, but often leave the ends, as they're less noticeable. $12.00 for the car, a buck or so for the steps and grabs, and another $3.00 for the Champ decals.
Red Caboose PRR X-29 boxcar - I was lucky to pick up a half-dozen of these undecorated kits at the LHS for about $8.00 each, normally around $25.00 or $30.00 each in these parts. I spent about another $4.00 per car for metal steps and grabs, and the C-D-S lettering, but had to plug the holes cast into the body for these parts, as they were oversize in order to accomodate the plastic detail parts included with the kits.
Here's the Train Miniature version of the same car - available used for 3 or 4 bucks, plus another $4.00 for steps, grabs, and lettering. The doors are from the scrapbox.
Here's another TM, modified with double doors: (about the same cost)
Athearn reefer - $2.00 used (it was damaged), plus another $6.00 or $8.00 for steps, grabs, Grandt Line door hardware, 6 extra hatches, and some C-D-S lettering:
Next are a couple of LifeLike (Proto-no-thousand

) 36' reefers. $.98 each from the "used" table, plus a buck or so for steps and grabs. The ladders on the first car, plus the brake gear and trucks on both are from the scrap box.
Even premium-priced kits (or r-t-r) can be improved with the addition of some detail parts. I added metal steps and grabs to this $30.00 Red Caboose reefer, and redid the brake gear for under a buck, although the hole for the grabs had to be first plugged with styrene rod, then re-drilled for the finer wire parts. New decals, from Champ, were another $8.00.
This Tichy reefer came with everything except the paint and lettering, for about $25.00. I substituted the trucks shown, and got the lettering from the same set as used to letter the previous car - which also did an additional two cars - only $2.00 per car.
This car is a r-t-r Proto1000 car from LifeLike Canada, which normally sold for $39.95. However, the initial batch was mis-lettered at the factory, so free replacement bodies were offered, with the correct lettering, in exchange for the return of the originals. The mis-lettered originals, bodies only, were offered at the LHS for $2.49 each, so I snapped up all six which were available the day that I was at the store. I would've bought up to two dozen at this price, had they been available, as this was one of the most common cars in the era that I model. I removed all of the lettering, and all of the grabirons (36 per car) and corner steps (6), then plugged all of the holes, and re-drilled for wire parts. I also built new roofwalks (those on the model were 6" too short at both ends), and fabricated new corner grabs from wire. I built floors from .060" sheet styrene, and underframes from styrene strips, then added new Proto trucks and Kadee couplers. For a
lot of work and about $12.00 per car (including the cost of the body), I got 6 accurate cars that would've otherwise cost about $240.00, far beyond what I'd be willing to pay.
The Pennsy reefer shown below is a Walthers r-t-r car that was commonly seen all over North America, so I bit the bullet and purchased one for over $30.00. Even it benefited from some detailing work on the ends and roof, along with a more accurate version of the brake gear. I changed the car number, too, just to make it different from the others out there.

Total additional cost was only about $2.00.
You can also find cheap passenger cars among the "used" stuff. I got a half-dozen or so Athearn Pullmans for about $4.00 each, and for a couple more dollars per car, created a bunch of wooden head-end cars. The Central valley trucks on the first car are from my parts supply, but all of the others are the stock Athearn metal trucks:
There are many bargains to be had, no matter what era you model, if you take the time to look and are willing to do the extra "work" required. I've even found many suitable cars at garage sales, available, literally, for "pocket change". How they look when you're finished is entirely up to you.
Wayne