The construction manpower is about 18 person-hours and the cost of material (principally the aluminium foil) is about $3.
There are many ways you can modify this model. You could e.g. use only one mirror, or maybe five. You could add a tracking system to automatically follow the sun. Or instead of parabolic mirror you could use so called Fresnel mirror for the same result. Litterature offers many ideas of design and use of parabolic solar concentrators, beginning from the war machines of ancient Greece.