Kind of ironic, given how the show has traditionally been associated with a shoestring budget.
Yeah, but that's always been the case, certainly for people living outside the UK. It sounds dirt cheap by today's standards, but in 1988 the cost of the Target novelisations distributed in Canada skyrocketed from about $4.95 to $7.50 for a time. I remember seeing "Time and the Rani" in a bookstore for that price and being shocked (I didn't buy a copy of it for years), because at that time NO standard paperback novel cost $7.50!
Of course, today it's considered a treat to find a paperback for less than $10, especially with that horrible and uncomfortable-to-read "long and skinny" format paperbacks that were introduced a few years ago and are spreading like ebola.
Still, I don't consider DW spinoffs to be any more expensive than others. It costs about $30 in Canada for one of the Target audio readings AudioGO is putting out, which isn't much more than similar unabridged, multi-CD releases. The Big Finish releases I think are priced quite reasonably considering that, once again, this is a small, independent company that hires some pretty heavy duty talent to record its plays and has managed to get virtually every living classic series companion and (now) Doctor to reprise the role. I consider their pricing to be quite reasonable, considering these aren't volunteer operations.
Just as with Star Trek, it's impossible to get everything. There's just too much and no one can afford a complete set. The best you can do is pick and choose. The wonderful thing about Doctor Who is, of course, that you can: if you decide you don't want/can't afford, say, the Fifth Doctor audio adventures and just want to stick with the Seventh Doctor ones, you can do so. And things like the Companion Chronicles (mortgage your house if you have to, but buy "Peri and the Piscon Paradox"!) are mostly standalones.
Alex