You can use either one. Strictly speaking, "sell-out" is a noun being used as an attributive, i.e., in place of an adjective. English grammar allows this, and it is often done. "sold-out" is the past participle of the compound verb "sell out," also used in place of an adjective to describe something. If you sell out a performance or show (sell all the seats) it is a sell-out, and it has been sold out.
You could just say, "The pantomime had five sell-outs with revenue of £3,000."
In relation to any kind of performance or exhibition, a "sell-out" means a sold-out event, making "performances" more or less redundant. With "sold out," you could say,
"All five performances of the pantomime were sold out, with revenue . . . "
I vote for "sold-out" because the performances were in the past.
We expect a sell-out* performance tomorrow. We had a sold-out performance yesterday.
*Or "sold out." It would also be idiomatic to "expect a sold-out performance tomorrow." That's because you are describing what you anticipate will have happened by the time the performance is over.
It's also because "sold out" is a fixed expression in English meaning exactly what it says. Meanwhile "sell out" has a second, completely different and negative meaning, so that some people might shy away from it.
Edited to add: Come to think of it, a person who "sells out" has "sold out," so "sold out" could have the same negative connotation. I guess, to me, "sold-out" is just more common than "sell-out" as an adjective to describe ticket sales.