I think total I spent on my setup was $350. But things have shot up in price!
Here is a 10" box that is ported. I have the 12" version of this paired with a alpine DVC sub.
https://www.amazon.com/Qpower-Single...d_i=B00NHL79QM
Choose your flavor of sub and make sure to get the dimension of mounting depth.
Then figure out an amp.
I bought this amp $150 a couple years ago..and wow..this has gone up in price so much!
https://www.amazon.com/Rockford-Fosg...2-63e904010ad0