What is the cheapest GPU for AI?
There is no single cheapest GPU for every AI workload. A lower-cost card can be a good choice when its VRAM fits the model and it is used often enough to justify ownership. For short or uncertain jobs, the cheapest option may be a rented GPU because you avoid idle hardware, power, and maintenance.
Is an RTX 3090 or RTX 4090 better for budget AI?
The RTX 3090 can be attractive when its 24GB of VRAM is available at a large discount. The RTX 4090 is usually faster and more efficient, so it can be the better value when training or inference time matters. Compare total hardware price, electricity, warranty, and expected hours rather than comparing speed alone.
How much VRAM do I need for ComfyUI or Stable Diffusion?
About 8GB can work for smaller Stable Diffusion workflows, while 12-16GB gives more room for SDXL, ControlNet, higher resolutions, and multi-model ComfyUI graphs. 20-24GB is a more comfortable budget tier for larger workflows and batches. Check the exact checkpoint, resolution, and extensions before buying.
Is a cheap GPU for AI training different from one for inference?
Yes. Training and fine-tuning need room for gradients, optimizer states, activations, and batches, while inference mainly needs model weights, KV cache, and request concurrency. Quantization can make inference practical on a smaller GPU, but training often benefits more from VRAM capacity and memory bandwidth.
When should I rent a GPU instead of buying one?
Rent when usage is bursty, the model size is uncertain, you need more VRAM than a local card provides, or the workload must finish quickly. Buying can make sense when the GPU will run regularly, the software stack is stable, and power, cooling, support, and resale costs still fit the budget.
Methodology and official references
GPU Cost's comparison rows are database snapshots. Hardware values describe the GPU, not a complete workstation or server quote; cloud values are observed provider rows and can change with region, capacity, billing model, storage, and platform fees.
Verify the final product specification, provider quote, availability, and software compatibility before purchase or a long training run.