To be exact about it, model the cost across the whole route, including the parts that are not the drug: consultation fees, laboratory monitoring, shipping, and the tests you will pay for yourself.
Denials come in two flavours and it is worth identifying which you have. A criteria denial means the submission did not evidence something the criteria require, and it is fixed by supplying the evidence. A formulary exclusion means the plan does not cover the drug at any level for any indication, and no amount of clinical documentation changes it — the route there is a formulary exception request or an employer-level appeal.
Twelve-month cost modelling, laid out: take the monthly product cost, add consultation or subscription fees, add laboratory monitoring at your chosen interval, add shipping, and then adjust the product cost for actual delivered content and dead-space loss. The route that looks cheapest per vial frequently is not cheapest per twelve months, because the fee structure and the monitoring dominate at lower product costs.
The caveat is jurisdictional. Almost everything in this area is specific to a country and often to a sub-national jurisdiction, and a confident answer that does not name a jurisdiction should be treated as describing somewhere else.
Model twelve months, not one. The fee structures are designed to be compared monthly.