I'm not going to add anything to what the others have stated but since it sounds like you are a little new to the hobby and not aware of the costs of slabbing,
there are really the only two reasons to slab a coin
1. its a rare coin that needs authenticated and preserved
2. you are planning on selling the coin and the cost of acquisition plus the grading fee's would warrant it without chewing up all your profit. I would suggest setting a threshold like $250
if you are not familiar with grading here are the costs:
PCGS charges a minimum of $69 for a subscription other subscription levels include grading vouchers though so you could reduce these costs. add to the subscription cost, per coin grading cost which is a minimum of $23, shipping & ins both ways (1-4 coins is $27 if the total value is under $1000)
NGC - economy grading tier is $22, plus $10 handling fee, plus $28 for shipping (1-5 coins) and insurance both ways.
ANACS - Economy - No Gold: $18 per item for items valued up to $500. plus $29 for shipping (1-4 coins) and insurance both ways.
CAC - $99 subscription ($50 grading credit), economy grading $15, gold $28, $40 shipping/handling/ins
i don't slab coins for these reasons especially the cost involved. I don't know why this is so popular today. just making the grading companies wealthy