You need to meet certain conditions to grasp quality and that might be expensive but other than that, proper gear means less work. If you dont than your reasoning applies and it doesnt mean you can be less creative/productive.
Yes you can cut corners with software but recording the perfect take with a mic chain suited to the vocal's characters means you often dont have to do a lot to fix up. The way i look at it, if i need to do much processing/editing on the recorded material, you fucked up. If you dont have the proper monitoring environment than how can you be critical if you're not going to notice artifacts/distortions in sound. Dont mean to sound derrogative but making assumptions to what sounds good in such conditions is kinda random.
That being said, if you got knowledge, then often very good things can be had rather cheap. Upon certain level there's no escaping big pricetags for even the smallest setup (mastering).
The idea of a booth is to keep unwanted noises from your recording, its that simple. No need to explain why that is. It doesnt mean you "need" a fully treated room to record (to mix is different) as the most important thing is to keep your distance from the walls (ergo, prevent reflections coming back at the mic, often the ones coming from behind you).
Imo, the best thing you can do is to use bookshelves, recordshelves or blankets as diffusers placed @ 1/3 roomlength behind you. Heck, the 38% rule/guide might even apply and the SE reflection filters also do a good job.
