For not a lot of money, for coins in dry sand the Tesoro Compadre is tough to beat. In the dry sand it will find as much treasure as any other machine regardless of cost. it's American made and comes with a lifetime warranty. You will not find a less expensive detector that can get the job done.
WE use two Tesoro machines for dry sand hunting - the Compadre and the Vaquero. The Vaquero is overkill for dry sand. Another advantage of these two machines is their quick recovery. That is, their ability to read targets in quick succession.
Lastly, there is no inexpensive option for hunting wet sand or water. However if you want to step up, the Minelab Sovereign GT would be my recommendation. No longer produced but still available in some places. Second would be back to Tesoro with their Sand Shark. The Sand Shark is a reasonably priced wet vac at the beach.