Here are some measurements: http://www.ubercart.org/comment/12308/Re-devel-module-has-setting
There are other methods for increasing PHP memory that don't involve .htaccess, shown at http://www.ubercart.org/faq/3072

Ubercart is big, for sure - bigger than Drupal itself - but that's because of all the features.Your problem is at least as much due to all those other modules you have installed as it is with Ubercart. 21+ MB without Ubercart is very large! If you really need to use all those modules, and the alternatives in the FAQ above don't work for you, then it's time to look at better hosting solutions.

Let me get on a soapbox for a minute... If you're setting up a site that sells things, you can afford to spend more than the $3.95 a month a shared hosting site costs. Just do the math - if your site goes down for one day, how much business will you lose? More than a VPS costs per *month*, easily. If you expect to make any sort of income from your web site, it just doesn't pay to deal with bargain-basement hosting companies. Find a package where you have complete control over things like PHP version, memory size, compiled-in options, MySQL version, etc. etc., and pay for the privileges and reliability that brings.