Only expensive in Russian forums because suppliers on Russian forums are mostly working on getting USA lines, so ending up with less UK results. if something is rare then it is always more expensive (supply and demand). Though, they are cheaper in English forums where there is competition because of many suppliers are working on getting UK results.
On the other hand, i am not saying i will pay $5/10 for good private lists. Can be negotiable for sure, and i respect quality work and wouldn't hesitate to praise it. But, nowhere near $50, as i am already getting private lines for way cheaper than $50 and below $30, so no point for me paying $50 and around. It is just that i am trying to build a larger supply chain.
If you are already selling them for above $30/$50 per 1K then it is very good for you and i am really happy for you, go for it my man.