Well you can use the same IP but I'll assume that you're selling fake goods. And therefore, if one account gets blocked they all will become blocked due to 2 reasons. First you have linked them all to the same paypal. Second you have probably used the same browser, haven't cleared your cookies and most importantly haven't changed your IP. So therefore there is little value in multiple accounts if you aren't going to keep them all seperate. As soon as you log in with the same IP the accounts are linked forever.
Plus I know it's not against the TOS to have multiple accounts, but having more than one account for the purpose of avoiding ebay limits is perhaps the fine line that blurs the distinction between being within and breaking the TOS.