It's pretty common even for the ones you see for $999.00 on everlast and title boxing's site. It will cut vibration down immensely. One thing to note on the ibox platform from balazs is that it comes with a S swivel. Some people like them for doing tricks and such but other than that if you get a swivel like the Title delux pro swivel for $29.99, you can't beat the smooth action of it. I actually like it better than the platinum pro swivel for $39.99. Reason being is that it is shorter which makes the rebounds faster. You will have to drill 4 new holes for the swivel but that is easy to do if you have a drill, no what I mean? And it is definately worth it. If you are worried about sand spilling out maybe another medium can be used. Or triple up on the bags. Hope this helps with your choice.
Here is a link to the swivel I am talking about.

http://store.titleboxing.com/speed-b...s-swivels.html