Yes there good, i'm gradually changing to this type of test kit from tetra, as they are cheapers and do more tests than tetra, good value for money with having three tanks to test.
I bought mine off ebay for around £19 including P&P although I have seen it in one out of four of my local fish shops for £16. Don't think you'll get it any cheaper but it's an essential part of fish keeping especially if you intend to do a fishless cycle.