Formula to price product by quantity variation

I want a formula to provide pricing for the following:
-The base price is $240,000, which includes up to 250 (this number is sockets, in case you are wondering)
-if the number is from 251 to 400 I need to subract that number from 250 and then multiply by $680. Then I need to add $240,000
-if the number is from 401 to 600 I need to subract that number from 250 and then multiply by $540. Then I need to add $240,000
-Lastly, if the number is over 600 I need to subract that number from 250 and then multiply by $400. Then I need to add $240,000

Here are some examples results:
-If there were less than 251 sockets the price would be $240,000.
-If there were 300 sockets the price would be $274,000 (((300-250)*$680)+$240,000)
-if there were 700 sockets the price would be $420,000 (((700-250)*$400)+$240,000)

Try

=240000+((A1-250)*lookup(A1,{0,251,401,601},{0,680,540,400}))

where A1 holds the socket value