The Miami series are probably the "It" thing in shoulder holsters. Way way back when, they were called the Jackass, then Miami Vice came out and made them famous. Thus the name change, and Miami reference. At least that's the story.
Like any other carry position, shoulder holsters will work for some, but not others. I can use the Miami Classic II shoulder system, and have one. The Miami Classic (not II) would be less comfortable given my size, I imagine, and the Vertical system even less so. I'm not small, and reaching that much futher for a vertical pistol or bottom opening magazines might be a stretch I can't make without months of nothing but rice cakes.
A lot of custom leather holster manufacturers will make a shoulder rig as well, and they all but copy the Miami line. I haven't done a LOT of research, as I went with the Miami Classic II pretty quickly- but you're probably trading a little leather quality from them, for Spider Harness Flexalon Backplate thing-a-ma-jig. I think if I were doing it again today, without the ability to test them, I'd still go Miami for the Whatchamacallit. If I were any bigger than a touch over 6' tall and about a 60 Regular coat size, I might have to go with a custom maker to get the shoulder harness in the size I need.
If by "$50" version you're talking about an Uncle Mike's style fabric thing... I wouldn't get one of those, but I'm sure they're good enough for others. It may be unfair but but there's a fair degree of bias against the cheap/nylon stuff because so many have bought cheap, found out it wasn't good enough for them and had to go out and buy again- especially for Inside the Waistband style holsters that need a stiffened opening for one-handed holstering.
And to be fair, despite dropping the money on a Miami Classic, I've never been outside wearing it. I've put it on, and adjusted it so I can, but I always seem to go back to my Kramer IWB. Part of it is- I don't use it so I'm not used to it. The other part is what I'm not used to. Without the tie downs it flops around too much. With the tie downs, I can feel it tug everything I bend/sit/stand.
As another shoulder holster option, Blackhawk! has made a rig to work with their Serpa platform. Nylon harness, plastic mounting bracket like thier beltloop, drop leg, and Paddle mounting systems. I got one for free with the drop leg system I picked up. That's about all I would have paid for it. Serpa stuff is not as compact and concealable as leather/nylon to me. If I want concealment I want it to be great. Rarely I won't care about concealment (like the Drop Leg) during hunting or the like so it's utterly un-concealable. I personally have no interest in a hybrid type in there that I can conceal in a pinch.
Your mileage may vary, in which case, a kit with a Serpa Paddle, Belt Loop, and Shoulder mount may be the ticket One holster, three mountings. 2 Minutes with an allen wrench.
My personal choices:
Inside the Waistband a Kramer leather IWb #1.5 or #3 (I'm west Coast, if I were East Coast, thee was a place in Florida that had basically the same stuff)
Miami Classic II Shoulder System
Blackhawk! Serpa Drop leg system also available in a STRIKE kit (which I picked up, then purchases a Serpa Holster that fits non-Berettas) cheap on Ebay
My next holster is most likely to be a Multi Holster 2 in 1 that you just change the mounting hardware to flip flop inside and outside the waistband in Kydex (I want to try a Kydex IWB for easier re-holstering. Plus they can mold for a laser, so I may get it for my railed 1911 with the railmaster.
You've got a real gun belt too don't you? Not a cowboy Action shooting Wild West movie type, but a plastic reinforced or horsehide leather gun belt designed specifically for the weight of a pistol, holster, magazine carrier, and so on?