Right now, the issue is not so much a dollar cost, rather the physical feasibility of either testing, or the availability of N95 masks.
1) To run a testing programme, a jurisdiction needs the testing capacity, as well as the organisational capacity to administer tests. In many jurisdictions, neither capacity exists at the time of writing (mid-April), although efforts are being made to put them into place. For example, see the California re-opening plan discussion: link to California plan.
2) Requiring N95 masks to be worn is not feasible in anything other than a very small jurisdiction so long as they are in short supply. In the near run, all that could be realistically mandated is the wearing of any covering, including reusable cloth face masks. The cost of wearing such masks is quite small relative to the cost of clothing, which is already mandated by indecent exposure laws. As such, the costs of masks is not a material concern.
The cost issue is the cost of enforcement. Mask-wearing is only one aspect of physical distancing mandates that have to be enforced. The cost of enforcement is not likely to be material when compared to the costs of the loss of productivity (including closing some activities entirely) due to physical distancing rules. That productivity loss is the main concern of economic analyses at present, and there is currently very little solid information to work with.