The cost of ovulation tests depends on the brand, type and where you live.
In Spain, the Unitest test strip format is the most economical. A box with 25 strips costs about 11€ and a box with 50 strips costs about 20€. in contrast the Clearblue ovulation test with 10 tests is priced between 20-30€, so it is a bit more expensive.
In the UK a box of 20 tests of the Clearblue type costs between £25 - £50 depending on the brand and sensitivity of the test. Test strips are priced at around £10 for 50 test strips.
In the USA the digital tests cost around $40 for a pack of 20 and, the more economical test strips you can find for approximately $15 - $20 per box of 50.