Shapeways

Shapeways has a store page by provider. There are a lot of Star Trek models on there however they are unlicensed and so can disappear when cease and desisted by CBS. There is one licensed Star Trek model producer that is Amarillo Design Bureau ADB the publishers of Starfleet Battles SFB. They offer several scales 1/3788 which is compatible with Starline 2400 (gray PA12 D7 $11). 1/3125 which is compatible with Starline 2500 (gray PA12 D7 $13) . The also have a 1/7000 fleet scale called Elite (gray PA12 3 x D7 $19) . A display size 1/2500 scale called Prestige (gray PA12 D7 $29). Finally the Omni scale is used for monsters and stations a planet killer is $50. As the scale gets smaller the miniatures get bigger and cost more. 

Shapeways is a print on demand service, you browse their library of models order the prints and they will be delivered to you. Prices are expensive and depend on the material you use for your print. The best material for miniatures is currently Tan Fine Detail Plastic or TFDP, this is however very expensive a single ship is $40, which is ridiculous. There are cheaper materials but they don't make for very good models. The best compromise is probably Gray PA12 Multi Jet Fusion Plastic which is about $16 a miniature, the finish is slightly grainy. 

To be honest the cost of a small fleet from Shapeways you can buy your own resin printer, resin and curing station and print your own fleets using free models. The only models that are not available are the ADB Starfleet Battles range which you can only buy from Shapeways or get them the ADB store if you want legacy metal miniatures. Those with the skills can model their own ships from schematics or pictures using free software such as Blender.

There is also a secondary market for Shapeways models on eBay and you can pick up out of print models for example.