WOW. That's alot let me attempt to field all your questions.
1: YES, a Good Artist (the only kind you should consider!) CAN tattoo over scar tissue. However, they'll want you to wait til scar tissue is fully healed. Couple ofd years is usual answer. I HAVE scars. I have one going right through middle of my left sk8/arm. Check out this pic from last Anthem session on Fri afternoon, note the line in my left forearm where I don't have any hair visible.
Now, I know you think yours is worse/more visible but it's also MUCH newer! My scar is 10+ years old. And now it's like it was never there:
Scar is/was through bottom of boot but you can't tell. Can you?
Just wait awhile til it's good & healed.
As to price....well that depends entirely on the Artist. It's almost always hourly. So how fast they are (& how still you can sit for uninterrupted periods they "Cheaper" it'll be. In my case it was $100/Hour for 9 hours. But I wasn't charged for the initial consultation 2 weeks earlier when we talked about what I wanted & he took pics of my sk8s. Or his time drawing up the original designs. So I think I got a Killer deal. I mean, they're gonna be there FOREVER, right?! And I wanted them to look like I wanted them to look AND look Good.
So, does that answer your questions?? Hope so.