Given that

$$ cost\quad of\quad Y_p\quad test=\$2,500 $$

$$ cost\quad of\quad Sam\quad test=\$50 $$

$$ Total\quad volunteers=1000 $$

Then total cost can be calculated as

$$ Total\quad cost=1000\times2,500\$+1000+50\$ $$

$$ =\$2,550,000 $$