If it's counterbored it's not worth anything in my opinion, unless you're a collector and it's a rare date or ex dragoon or something. If the bore is in good shape, then it's worth whatever someone will pay for it. If you look on gunbroker there are dozens of 91/30s hex and non for 250 and up, and not one of them is selling. It also depends on if it comes with bayo, sling, etc. In any case, I can guarantee you the ammo is worth more than the rifle itself. I would pay 180-200 for a non counterbored, all matching 91/30 hex with all the accessories.
Just for context, I recently bought an unissued condition M44 with all matching numbers (not force matched) for 275, and a force matched 91/30 sniper that's all correct for 750, and I feel like those were reasonable prices. It's important to distinguish between what people are asking as opposed to what they are getting. Lots of jokers bought up nasty shot up mosins for 80 a pop five years ago, and now they're thinking their ship has come in. A sucker is born every minute so I guess they might get lucky (or rather someone else gets unlucky) at some point, but like I said they're mostly just wasting everyone's time.
Also keep in mind that gun prices are going down right now. I honestly think Mosins will go back down to near where they were five years ago, especially now that the ammunition isn't cheap anymore. They're not collectible (for the most part), they're not good shooters, and the ammo ain't cheap no more; so people are bound to get sick of having a bunch of useless old shot up 91/30s cluttering up their safe. If a mosin is not pristine and all correct then it's just not worth having anymore.