In a normal market, it would fill within 1-5 pennies, more than likely.
While that’s “big money” to you and I…it’s not big money in a very liquid stock. For instance, IBM trades like 6 million-10 million shares per day at around $120ish per share. So, that’s a ton of money that changes hands each day in IBM.
But James is right that FXY and E would trade less than that. Liquid, yet much less liquid. Doesn’t matter for the sizes we trade in, but it would matter on the institutional level, investing billions of dollars.
There’s not concerns on an individual level, mainly at the institutional level.
As a broker, I deal with some $20 million and $100 million accounts (rarely) and there were no problems getting in and building positions, etc. So I wouldn’t give much thought to fills, at our levels.