WBShop.com has the original Red Dwarf Series I-V (Seasons 1-5) for $14.99 each with Free Shipping on all DVD orders.
(These are normally about $28 at most retailers)
If laughter is the best medicine, then you could pick up all of these for less than it cost me to go to the doctor once.
Red Dwarf is arguably the best comedy Sci-Fi ever released... and It's funny. Really, really funny. Seasons 1-5 are probably the best of the series.
Alternatively, Amazon.com has the entire original Series 1-8 for $84 (which is just over $10 a season with free shipping)
(fyi, there are 8 original seasons of Red Dwarf, plus a recent TV movie and a new Season 10 with a reunion of the original four cast members)