Is the DGX Spark worth the money?

I've seen a lot of DGX Spark discussions here focused on inference performance, and yeah, if you compare it to 4x 3090s for running small models, the DGX loses both in price and performance. The Spark actually excels for prototyping Let me break it down: I just finished CPT on Nemotron-3-Nano on a ~6B tokens dataset. I spent about a week on my two Sparks debugging everything: FP32 logit tensors that allocated 34 GB for a single tensor, parallelization, Triton kernel crashes on big batches on Blackwell, Mamba-2 backward pass race conditions, causal mask waste, among others.