I would like to know key values regarding Guitar Effect Pedals in
North America and Europe.

Specifically I'm interested in the approximate number of units sold
and the total turnover value from a retail point of view.

Usually the retail for used goes for an over inflated price. Your most
popular effects go for higher prices (Stuff like what the big bands
have listed as their equipment, or time tested equipment such as stuff
used by more famous musicians such as Hendrix etc...)

Your most common price lately for Boss hardware is around $90-$160 for
stomp boxes, used you could get stuff like that online for as little
as $40-$70.

I don't know what you mean by key values, but the thing that keeps the
price up is usually 1.) Popularity of the product, 2.) How proven the
product actually is and how well it performs.

A lot of manufactures are coming out with stuff that seems like it is
way over priced lately, you don't get an ac adaptor most of the time
without spending an additional fee of about $30 for this peice as
well. For a multi tap effects power rig you could spend from $100-$400
alone...

Not sure if I gave you a good enough answer but I hope it helps.

I am looking for figures explaining the market from a company perspective. 
The key values i'm looking for are just the total amount of money used
on guitar effect pedals on the American (and perhaps European) market
by
 1. consumers
 2. retail stores for resale to consumers
 3. effect manufacturers for sale to retail

The number of effect pedals bought each year is also something I am interested in.