Assuming you're willing to use your existing road bike on a trainer, you have several options in your budget ranges.
A wheel - on trainer (example: Tacx Flow) will set you back around $370. It's a smart trainer, but you will have tire wear (use the extra budget $$ to pick up a spare rear wheel with an indoor trainer tire on it and a cassette) and there is the need to calibrate it. The tension on the rear wheel has to be set and checked regularly, and there is always the possibility of tire slippage on the roller drum. That being said, I use an older model, wheel on Tacx, and I'm happy with it.
If you're willing to go high budget, consider a direct drive trainer. A Tacx Flux S will set you back around $750, a Tacx Flux 2 around $900, and at the top of your budget, the Wahoo Kickr at around $1200. I'm sure there are other brands and models, so look around and read reviews.