LOL. Okay ]\/[onsters let me tell you guys about king bettas and true giant. I'm a long time betta keeper with loads of experience from fighters to fancies.
King bettas (a name use to sell in the market) are basically just regular bettas that get a tab bit larger(mainly due to feeding and space), they are not the true giants. A full grown king bettas gets about 3" and that's about 10-12 months old.
Now lets talk about the true giant bettas. At the age of 5 month, they are about 3"-3½" long and at full growth if kept in 20 gal + they will push everything 6"-7". The cheapest I see true giants goes for is $20 ea. Higher quality grades of giant push everything to $40-$80 ea.