The good news is that charging more to use data in one way (with a hotspot app) and not in another (web browsing or a non-hotspot app) is almost certainly a violation of the FCC's new net neutrality rules. Net Neutrality prohibits mobile operators from blocking legal apps or services or charging more for some types of traffic than others. As long as pro-big business politicians don't succeed in repealing the FCC's net neutrality rules, I believe that AT&T will eventually be ordered to stop charging extra for Cricket hotspot use. Unlike AT&T, T-Mobile, apparently recognizing the illegality of treating hotspot use differently than other data usages, removed its restrictions on hotspot on June 12, 2015, the day the Net Neutrality rules went into effect.
Related post: T-Mobile to Allow Hotspot on All Prepaid Plans With Data