domain purchase is nowt – maybe a tenner a month at most
but i doubt you’ll get much for £1k.
I used to work for a commercial software house, doing car dealer management systems – ok it’s a bigger deal than what you’re after – but 10 years ago the going rate was £450 + VAT per DAY of development time. NB that’s the company’s price; they didn’t pay us developers anywhere near that 😉
Obviously there’ll be a lot of smaller businesses out there that won’t charge anywhere near that much – maybe not even a quarter of that – but you might be better trying to find something off the shelf, if possible, that you can customise yourself with a small amount of training