Polydrons are great - and expensive... you will find them in several math
supply catalogs. I think they average out to just under $1 a piece - but
they do last forever... I have two large bins (from my math years) - they
last a long time, I haven't had the hinges 'wear out' at all (some things I
have on my free time shelves can't take the wear and tear) - the kids love
them.
ETA carries
set of 50 is $37.95
set of 90 is about $70
set of 438 is about $335