You won't find that Triumph branded Mobil racing oil anyplace but at a Triumph shop and $50 is about the going rate for it.
Many of the guys on this site are using either Mobil MX-4T which you can get at many AutoZone or Checker stores for about $8 a quart or Amsoil which sells for around $7 a quart. Filters can be cross referenced as well though be careful you get what you pay for to some extent.
Check out some of the on going threads on oil and filters posted in the Tech Talk section.
Keith
