I think you have some serious thinking to do. Browning already asked why you would want it in the first place with all the alterations. I would ask the same question. Simply to own a milsurp or something else?
This is a great site to ask questions. And you can ask them in the general milsurps forum at the top when asking about multiple rifles and thoughts/opinions.
In answer to your more specific questions. No $150 is not a good price for a sporterized
Arisaka
, especially if it is a last ditch which you mention in the title. Less than $100 depending on how sporterized it is. Last one I bought I paid $40 for and that's because I felt sorry for the owner. Ended up putting $260 into it so I'm not a real happy camper with it but it is at least presentable again.
You want a decent non-altered Arisaka, expect to pay about $300 to start although there are a few closer to $200 around. The mum will be missing but this isn't a bubba thing but a normal thing so not a huge deal. Add $100 for an intact mum.
If you want to collect milsurps, don't start with sporterized ones because a few years down the road you will be kicking yourself wondering why you bought the thing in the first place and why no one will buy it from you now.
If you want an inexpensive gun to shoot, that's different, but an Arisaka isn't a real good option because while the ammo is available, expect to pay about $40 for a box of 20. If you reload, that's not a huge issue. If you don't, it is.
A good starter rifle that is still affordable is a Mosin Nagant. Even these are in the $275 range now but they are usually complete, good shooters and the ammo remains cheap. For $50 more you can get a better rifle in one of the
British
Enfields. Ammo not as cheap but a more popular rifle and one easier to shoot. Carcanos are in the $200 range and ammo for them as long as it is a 6.5 is relatively easy to get and less than $20 a box.
If you are serious about collecting, get a guide of some sort. I like Peterson's military weapons guide myself.