Hello Sunnyboy.
Sowter transformers about 200 GBP for the pair (directly from Sowter), $100 for the resistors and caps. I use Eichmann female RCA's at $50/pair. The biggest advantage is flexibility: you can build in alternative resistances with a switch or two, and use that to tune your sound without the use of reactive tone controls. All in, less than $600; and that is using the type of premium components that few would use, unless they were charging 10x the price. After all, manufacturers have to make a living too.