Getting seven to grow out in a 75 should be fine.  I grew out six in a 40 gallon. Just feed light and keep the water clean unless your trying to grow them fast.
Price all depends on species.  Intermedia, xingu, and brokos will cost you $100+ for 3-4”.  Captive bred Kel, Azul, Orino, and Tems should run about 40-65 for 3-4”.  Farmies are cheap but I wouldn’t get them since they are likely hybrids. 
If you find something rarer like pinima or some of the rarer true ocellaris species, they’ll cost a bit more than the intermedia. 
WC bass come in waves.  
	
	
			
 
		 
	tcav88
 , Thomas, can you chime in on this question?