I made $19 an hour at Radio Shack in 1997. I would hope things have adjusted since, but My exGF made $26 an hour working at Ann Taylor. You can totally make $40k a year equivalent in retail.
Clarifying a bit, were either of you a (very) part time worker? It's not impossible to make 40k a year in retail, but not in seasonal, disposable employment.
Sure you can. Key Holders, and shift managers earn this part time in limited shifts. When I worked at Radio Shack I was in High School and earned because of commission.
My ExGF did well because it was a part time job and she was Very over qualified. She did a lot of tasks that required managerial experience, like supply re-orders, scheduling, time sheet reconciliation.
I actually almost took a Gig as a 20 hour a week Regional Manager for Ann Taylor when a gal was pregnant and wanted to cut her hours. I'd have been at $35 an hour and mostly doing administration tasks.
Similarly Geek Squad at best buy pays $25 an hour for MCSE's . Car Audio shops pay $35 an hour for qualified installers. There are lots of fill in and week end shift jobs that pay well.
If you are looking to supplement income you can't do better than working Holidays. Time and a half or double time for working days others don't want to adds up fast.
Do you start off as a key holder/shift manager? Or did you both start out making much less?
Now, with regards to Geek Squad and Car Audio shops, they rarely want a weekend and nights person, they want someone who ~needs~ the job.
It's possible if you stick them out, but I can't imagine people who don't want to put in years can just jump into these well above minimum wage gigs as easily as you claim.