Sean Dyche admits Burnley couldn't match the contract offer Aston Villa made to Tom Heaton.
Heaton joined Villa for an initial £8m on Thursday, having entered the final year of his deal at Turf Moor.
And the Clarets were not in a position to compete with the terms he agreed at the newly-promoted club.
Dyche explained the decision to sell: “I think it was just a simple equation, he got offered a nice offer for his family as well, which is important at his age, something we couldn’t compete with, and that’s another sign of the market - someone new to the Premier League can outpay us considerably.
“So he had to do that, and it’s right and proper players do that, and from our point of view, when it hit a certain mark, everyone agreed that’s the mark it takes to do the deal.
“But it helps that we’re well-stocked, I believe in (Nick) Popey and Joe (Hart), and will learn about Bailey (Peacock-Farrell), who looks like he has a real desire and hunger to learn.
“The club have a model, and sometimes when it hits a certain mark, the chairman says we’ve got to look at that, there is a reality to it, for a 33-year-old - I know how fit he is, but from the outside looking in, you don’t know those things, he’s 33, with 10 months left on his contract, so therefore it looks right.
“For me, you don’t want to lose your best really good players, but it’s not the first time it’s happened here, and it won’t be the last because of how this club operates.
“And it’s tough, I’ve said many times, it’s tough to find the right amount of input and right amount of output when we lose players, and that’s what we have to try and find.
“But I like the mix in the goalkeeping department, with Bailey coming in as well. And there’s a competitive mix."
Heaton was Dyche's first permanent signing, on a free transfer from Bristol City in the summer of 2013.
And he could go down as his best in time.
Dyche hailed his contribution: “I can’t say enough good things about him, a tremendous servant, both on and off the pitch, and all the work he’s ever put in pays him back, with all the performances he’s had, England etc, and really, every part of our success, he’s been a part of.
“He’ll be well thought of here, and anything he needs, I’ll certainly be there for him.
“But we’ve had loads of good players and good people, and he’s certainly at the top of the list, my first permanent signing, and I did get caned..."