Possibly nothing, but in this context, to me, "sell" means sell for a profit, while "charge for access" means charge just enough to cover hosting/admin costs. For something like getting my address or driving record, that's possibly the difference between $5 and $20 per request (total guesses).

I suppose it's the difference between "you downloaded this page to your RAM" and "you downloaded this file to your hard drive", plus how "access" means you're given a license to the data, and "selling" means you now own it as property.