Practice amplifiers are usually:
- 10-30W Solid-state / 3-5W valve-state,
- Combo.
So generally they are very affordable, especially for those on a budget, beginners, and those who want to practise at low volumes (like most of us HDB dwellers. Haha!). Some low-wattage valve-state amplifiers (like around 3 or 5 watts) are also practice amplifiers. I think the definition is based more on what it is used for - low volume practise or loud volume performing.
Mine is a 10W solid-state, made in Korea. Brand is Sound Drive. Not very well-known, but very good cleans. It can go quite loud for a 10-watter, but most of all, I can get likable tone at low volume levels. That's it's purpose as a practice amplifier, after all!