My experience with unneutered boys is that their box habits are pretty bad…. probably won’t get any better. Depending on the cost of living where you are, $300 might be about average, but hard to say. The House Rabbit Society reports the US nationwide average is about $250.
You might be able to find a lower cost though, so it would be worth calling around. You of course would want to make sure the vet is still rabbit savvy though.
I’ll also add, that if they are living together in the same enclosure, there is a good chance that they will start fighting when they hit puberty in full force, so you may want to separate them before that happens. (With your set up, would prob be easiest to divide their room in half, with a buffer between the fence so they cannot nip through the bars). Then once they are neutered and hormones settled you can go through the bonding process with them. Buns can hold grudges, so bonding might be easier if you separate them before they start acting aggressive towards each other.
The marking all over the place could also be linked to them marking towards each other since they aren’t bonded.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.