To say a band is just cashing in, and im talking strictly in the case of KGF in this case, is a little harsh.
As with most bands / musicians, they have different influences which then form their sound. That sound is then picked up by an audience.
I doubt when they started out, KGF targeted the 'northern soul scene' as their audience, perhaps more funk / jazz and general soul audiences at a guess.
Wouldnt say theyre trying to cash in; selling singles at £10 and only producing 500 copies. They'd clearly be cashing in if they had re-pressed the single following its success on the underground music scenes like this one.
I dont personally know the band (or any associates) so this is only an assumption, but i would suggest that the band ARE in fact showing an appreciation for soul music, as you can hear their 60's/70's soul and funk influences in music they produce, would hesitate to say even emulating their idols by producing music which capulate the great sounds from yesteryear.