They are not expensive wherever you buy.

I have just looked at some of my usual bulb sites for this item. Seemingly it has been a bad year for Tulipa sprengeri and many outlets have none for sale! The best I can find, £4.50 per bulb is Broadleigh Nursery:
http://www.broadleigh-bulbs-autumn.co.uk/cgi-bin/cp-app.cgi?usr=51F4348025&rnd=1011709&rrc=N&affl=&cip=81.158.183.12&act=&aff=&pg=prod&ref=tulipsprengeri&cat=tulips_alphabetical&catstr=HOME:spring_flowering:tulips:tulips_alphabetical