A long guts buys the in-the-money call and the in-the-money put, which together always contain the distance between the strikes in intrinsic-value. Pay more than that distance plus expected movement and you have simply overpaid; the extrinsic portion is what you are actually trading.
Nobody uses guts because they are cheap. They are used when the in-the-money lines are more liquid than the out-of-the-money ones, or when the bid-ask-spread on the wings is punitive. The cost is a much larger cash outlay and real early-assignment risk on the short version.
Example: XYZ at $50. Buy the $45 call at $5.90 and the $55 put at $5.70, total $11.60 against a guaranteed $10 of intrinsic. You have paid $1.60 of extrinsic for the move — compare that with the $45 put plus $55 call strangle, which is all extrinsic, before deciding.
Related: strangle, straddle, moneyness, intrinsic-value