Hmm, ur in USA im guessing. Im in the UK, but for me personally, i buy the
test strips of both OPK and HPT, one for cost and two because u can literally afford to POAS anytime u like without breaking the bank. Only downfall is u have to determine yourself if either are a + or - unlike the smiley face Ovulations tests u can buy.
Ebay are always a good place to buy, i get all mine from Ebay. But the UK one.
Ive just had a look around Ebay for u.