The modders are not using LOD models (Level Of Detail: The detail of the model changes to low when is far of camera and increases when is near) and not are optimizing the vehicle model meshes. The right way to do vehicle mods is easy to learn if we pay attention to the vehicles from the game, analizing its structure and taking note about how many polygons and texture dimentions uses. Around the world exists thousands of tutorials about how to reduce and create LOD models for videogames, and really the modders needs to apply that seriously to their mods, because is not just about performance and game graphics, the health of the hardware is also affected.

Wich is the good donation value for a modder?
I readed all comments and I want to start a modding campaign searching support for my work. The modding is hard and afortunally the tools are distributed free with donations support. Some modders do amazing jobs with clean rigs, good material treatment and without affect the game performance, meanwhile anothers do things without good rigging, no materials care and affects the game performance because not search and learn about the concepts and pipelines to do a good mod for a video game without damage its balance between visuals and performance.

About ripped contents, that is true, is from people who put their work and time professionally. The free models sites offer under "personal license only", that means is not redistribution allowed.

***Rockstar has a interesting article about modding in its games, and I show the next quote from that article:
***"We have always appreciated the creative efforts of the PC modding community and we still fondly remember the awesome zombie invasion mod and original GTA map mod for GTAIV PC among many other classics. To be clear, the modding policy in our license has not changed and is the same as for GTAIV. Recent updates to GTAV PC had an unintended effect of making unplayable certain single player modifications. This was not intentional, no one has been banned for using single player modifications, and you should not worry about being banned or being relegated to the cheater pool just for using single player PC mods. Our primary focus is on protecting GTA Online against modifications that could give players an unfair advantage, disrupt gameplay, or cause griefing. It also bears mentioning that because game mods are by definition unauthorized, they may be broken by technical updates, cause instability, or affect your game in other unforeseen ways."(Source: http://www.rockstargames.com/newswire/article/52429/asked-answered-the-rockstar-editor-gta-online-updates)

Personally I think: Do mods but do with the necessary like a native game component, and request support, not sales.

@Augur89 Is in my mod list to do and another TV series vehicles. Also I'll to include script with behaviours, weapons, vehicle realtime transformation (more realistic than the movie with micro animated hexagons) and AI vehicle support. The bad thing is not a near project for me.