I agree. The solution seller wheels are rated at 180Kg, Beachmaster at £200, but lighter duty wheels that you mention are typically 120kg which is much less.
I don't think price has anything to do with it. Solution Seller wheels are still priced as a premium product. The reason why Beachmaster wheels so expensive is that they are a premium price wheel, they are shipped from NZ, we have double exchange rate conversion to pay, we have to pay tax on import and there is often a lottery whether we have to pay the import duty handling charge. So what started off as I wheel that I could buy in NZ for equivalent of about £170, turns into a wheel costing a third more at the very least. Its not long since I could have got the Beachmaster wheels in NZ for about £100 - but I didn't know 5 years in advance that I needed a pair!
But you are right, quality is important which is why I either want to see a pair or get first hand information from someone who has seen them before I buy. Solution Seller have enough confidence in their product to offer a full money back on return including both shipping rates but even so, first hand knowledge from someone who has used them is more important than trial and error. Unfortunately these items are so new that no one seems to have used them yet. Thankfully I still have 3 months to find a suitable pair.