It's common in high-strength DIY applications to create the model you wish via 3D printing, disregarding the strength requirement. This model is then post-processed to remove layer lines (if so desired) and support material surface irregularities. The next step is to create a silicone mold from the positive model.

That mold can be used to cast higher strength resin which can be used repeatedly for multiple parts.

Silicone mold material is available with various characteristics. Some are high temperature, some will cast out in different hardness levels and durability is another factor of importance for semi-production use.

Costs are difficult to determine from your message or from my reply, but less difficult once you've printed your model and know the volume it occupies, as that will be the volume of casting resin required for each part. The cost of the silicone mold material will be a factor, of course, but will be spread over the quantity of parts created from a single (or multiple) mold(s).