The big issues with supercharging is, that to do it properly, you really need to decompress your motor somewhat, which really means engine out full rebuild. So once you add $5k in rebuild/major service parts, plus removing/reinstalling the engine ($1,000-$2,000), plus labour for rebuild (1,000-$2,000), THEN add on top labour to fit and tune the SC ($3,000-$5,000), it is a pretty expensive exercise, to say the least.
But with 300rwkw it would be all worth it