The Hidden Cost of a Wide Bid-Ask Spread
The price on the screen isn't the price you get
Every option quote is really two numbers: the bid (the highest price someone is currently willing to pay) and the ask (the lowest price someone is currently willing to sell for). The "last price" you see on a chain is just wherever the most recent trade happened to print — it can sit anywhere between the two, or occasionally outside them if the market moved since that trade. When you buy, you're paying at or near the ask. When you sell, you're getting at or near the bid. The gap between them, the bid-ask spread, is the cost of trading right now instead of waiting.
Why the spread exists at all
Market makers quote both sides of every contract and profit from that gap in exchange for taking on inventory risk — the risk that they buy from you and the price then moves against them before they can offload the position. The less certain they are about that risk, the wider they quote. Certainty comes from volume: a heavily traded, near-the-money contract in a liquid underlying gets a tight spread because market makers can offset it almost instantly. A far out-of-the-money contract in a thinly traded name, or a strike three expirations out that almost nobody touches, gets a wide spread because the market maker might be holding that inventory for a while.
A round-trip tax, paid twice
The spread isn't a one-time cost — it's paid on the way in and, eventually, on the way out. Buy at the ask, and if the underlying doesn't move at all, you're already underwater by roughly half the spread versus the mid-price. Sell to close at the bid later and you pay the other half. On a liquid, large-cap index option with a one-cent spread on a $3.00 contract, that round trip barely registers. On a thinly traded single-name option where the bid is $1.80 and the ask is $2.20, the round-trip cost is $0.40 on a $2.00 midpoint — a 20% tax before the position has moved a single tick in your favor.
That percentage matters more than the dollar amount. A wide spread on an expensive, high-delta contract might be a rounding error. The same dollar-wide spread on a cheap, far-dated, low-premium contract can consume most of the theoretical edge in the trade before it even starts.
Spreads compound across legs
Multi-leg strategies multiply the problem. A vertical spread has two legs, each with its own bid-ask gap — an iron condor has four. If each leg is quoted with a spread that's wide relative to its premium, filling the whole structure at the mid-price on every leg is unlikely; more realistically you're giving up some edge on each leg individually. This is one reason liquid, high-volume underlyings are generally easier to build multi-leg positions in than thin, low-volume names, even when the thesis is identical: the execution cost is structurally lower.
Reading spread width as a signal
Spread width isn't just a cost to budget for — it's information. A contract with open interest and volume that dwarf most of the rest of the chain will almost always have the tightest spread on that chain, because there's enough two-sided flow for market makers to stay confident in their pricing. A contract with volume that barely registers, far from the money, is telling you the opposite: thin participation, wider quotes, and a real chance that a market order fills meaningfully worse than the displayed mid. OptionScope's option chain view puts open interest and volume directly in the strike grid as micro-bars for exactly this kind of quick scan — a contract that looks cheap on paper but trades on scraps of volume is usually a contract with a spread problem, not a genuine bargain.
Before you enter
A few habits limit the damage. Compare the spread to the mid-price as a percentage, not just in absolute cents — a $0.10 spread on a $0.50 option is a much bigger tax than the same $0.10 on a $5.00 option. Use limit orders at or near the mid rather than market orders, and be willing to work the order instead of chasing. And expect spreads to widen briefly around the open and close, and around major news, even on contracts that are normally liquid — that's when market makers are least certain about fair value and quote defensively. None of this eliminates the spread, but it keeps you from paying more of it than the trade requires.