The covers are there to not only protect your own bike from damage, but more importantly to stop oil from getting on the track and potentially causing OTHER RACERS to crash
. Most experienced racers can tell stories of crashes as a result of other racers choices, a great example being an off-brand cheap oil filter failing on one of the bikes and spraying oil all over the track for quite some distance - that led to a 7 bike pile-up in the 'Kink' at Road America. The minimal amount of money that was saved on that oil filter resulted in ALOT of damage to the bikes involved, multiple injuries, and racers going to the Hospital.
As some friendly advice: If your just getting into racing there's some things you should just accept as being needed and haul off and bite the cost for the better stuff. If that means your going to have to skip an event or two in order to afford those things than so be it, investing
the extra money is the smart choice in the long run. In my opinion also don't skimp on personal protection for yourself, on your bike invest extra money on suspension upgrades, good brake pads, good tires, and quality bodywork (better stuff is often times more damage resistant and repairable).
Being a Tool & Die Maker of 21 years I can tell you the Woodcraft covers are high quality and worth the (most likely) one time investment per bike - the very reason I also have the Woodcraft covers on my bike. Good luck!