Let me tell you about the amp business
I can tell you there is NOT $4.5k worth of value in the product. It likely cost PRS 1/3 that price ( or less ) to actually produce. Assembled in USA doesn't mean much these days, as it is highly likely that much of the product is stamped out in China.
NEVER trust ANY company that says CUSTOM Transformers..... It costs WAYYYYYYY too much to produce a fixed # of transformers that are supposedly reverse engineered ( how has no other company done that yet??? ), and it is more than likely just slightly modified, off the shelf transformer, that has PRS stamped on it. Let's just say you could not sell an amp for $4k if it truly had custom transformers. It could cost nearly $1k per transformer for that. Keep in mind custom means you can't resale it, so you are dedicating R&D, along with tooling and training to make a couple thousand units.... You aren't doing that for $200 a transformer. The last set I looked at spec'ing out like that cost about $1k each.... Even at scale, you could not build an amp that is profitable with $1k worth of transformers in it. And what about future repairs?
There is a channel on YT that recently had to repair an MTS-15 with a blown output transformer. Guess what? No resale of parts to repair it with, so the repair tech had to order another similar spec OT to replace it with. Now imagiine a similar situation for your $4k amp.... That is what you WILL have. It would cost too much to carry an unknown amount of stock of replacement parts for an amp like this. Sweetwater is likely holding all the risk for this venture too.
This is a distrobution deal, and it is very likely that the price to build is fixed, allowiing Sweetwater to get enough meat in the game to take on the risk of holding stock, which was set at X number of units. When stock runs out, it is either re-up the deal, or stock is gone. With high dollar amps, it is hard to gauge how much stock will move. So why woudl PRS hold stock of replacement parts if it is not even certain the current stock will deplete? It is a gamble, which is why the amps are priced as they are.
I can tell you it does not cost much more to build this amp, vs. that amp if the part count, and type is similar. A Marshall Plexi, or a Freidman Plex, have essentially the same part count,a nd there is not a large disparity in production costs for one over the other, when you consider raw parts. Now, what it costs me, or Marshall to build it, is another story. I don't have the luxary of scale or quantity discounts. So what Marshall can build for $1K out the door ( not retail cost, but actual production cost ), would cost me double or more to do the same. Now which one is better is easy for me to quantify ( mine is.... ), simply because I know mine is built to the highest possible standard.
This is not to neigh say PRS, they are a business, and they have to make money, just as Sweetwater does. I am only pointing out the value for your dollar. PRS is making these to a price point, allowing Sweetwater to move them. The " Custom Transformer " thing is perhaps true, but may simply mean they put their stamp on an off the shelf part ( I call BS given the price )? I know that assembled in USA does NOT mean produced in the USA, it means produced elsewhere, and put together here. And lastely, that any amp with a distribution deal, is going to be a repair nighmare if things break, because parts will NOT be available. Which to me reduces value, because what good is a product that can't be repaired ( with the intended part )?