I'd say at least 15k$ but I'd say 25k$ is more realistic for quality that keeps your sanity in check.
2500$ is more of a good programers wage for two weeks and I doubt that a project like yours is done in that short amount of time.
However:
If you can live with analytics only, things might be a little cheaper. If we're talking about sending, canceling, amending orders or conditional orders that work off of fill confirmations, things can get complicated really, really, (really) fast.
There are so many failsave mechanisms to consider, what your program will do in case of disconnections from the client (e.g. no service for your phone), how fast it needs to be, etc. etc.
I once outsourced an autospreader for markets that off the shelf software wasn't connected to and it was a really simple algorithm. Quote market 2 off of market 1 and if filled in market 2, hedge in market one.
To get this baby up and running took half a year of swearing and losing money trading because there were a couple of bugs that were really hard to find. And when you work sub ms speeds, you can blow up your account faster than you can blink.
Do NOT underestimate this.sss