True, but it's worth considering what drives the market value of 3 and 10's up is that there are fewer quality ones relative to other positions which may be also just as important. 1 is arguably just as important position as 3, but most nations have more players who could do international level at 1 or 2 than 3. Even England who have the most depth in Europe don't have to have many injuries and their down to Henry Thomas, who Olyy has always said is a big drop from the top 2. Likewise, Wales are an injury away from Rhodri Jones at tighthead. New Zealand are lucky that Owen Franks seemingly never ever gets injured as well.
There's just a few excellent fly halves like Wilkinson and Sexton as well, who can dictate the whole team's way of play, and unlike a tighthead players like that would add more commercially to a side as a face to go on advertising which casual fan knows as well.