It's on Netflix USA, may be cheaper to use a VPN. Best TV series ever, about to rewatch as my wife has never watched it.
I was tempted by the DVDs but some very bad reviews of amazon of them, essentially not lasting and becoming defective after a period of time.
I used to pay about £40 per series back in the day. One of the best bits of TV ever.
Ooh, now I'm severely tempted.. I had the first two seasons already, I could nab the rest for £15ish including shipping - way cheaper than the £40-£50 the full box set is on DVD, even if it is second-hand..
Fantastic show, bought back in March for £65 on Sky Store.