Without knowing the specific model and the price they want, I cannot answer that. But, in general, it is something worth considering but you need to do some things before you do.

1. You need to look up the specific model, read reviews, and then see what it is selling on eBay for used. This is different than seeing what people have Buy It Now listed. You have to filter for Sold Items. You then will have a range of what it is worth to use in negotiating.
2. Then, you need to realize that the pawn shop is selling it to you as it came in. They didnt repair it or do a fresh install. The only thing they may have done is delete excess programs off the home screen to make it look nicer. When someone sells it, they just make sure it turns on, hooks to wi-fi, the buttons work and mouse works. They dont run diagnostics to see if the hard drive and RAM is healthy. They dont make sure it doesnt have a power problem or overheats. They also dont know if it randomly shuts off. So, you need to not only use it a bit but run some diagnostics. I am not going to go into that but Google about running diagnostics on a used computer and there are plenty of guides. Even better is find a video you like, go to the pawn shop pull it up on your phone and do it all right there.
3. So, you know what it is worth and you know if you have any obvious problems with the machine. A lot of pawn stores have price stickers and they have a lot of information. You can Google MarieLouise pawn shop and find out about how to figure out what they paid for it. But, more importantly, look for a date which is usually they date it came in. If it has been there for 10 months, you have a great tool for negotiation and they honestly problem want it out of there so they can put something else out. If you find out there are problems in diagnostics, it still may be worth considering. If the HD or RAM is showing signs of needing replaced, you need to use that cost of repair when determing the price you are willing to pay.
4. Then, you go negotiate a price. Never pay the sticker. If the laptop seems to be in good working order and they have only had it for 2 or 3 months, I would ask for $20 lower. If they have had it for a year, I would try to get 40% or 50% off. If it has problems such as needing a new hard drive, you mention that you will have to spend $50 on a hard drive.
   
   In summary, it all depends. It depends on the machine, the price, the value, and the person buying it and their technical knowledge. If you know very little about computers other than using the internet and writing papers, it probably is not a good idea. If you feel comforable running some diagnostics and replacing a hard drive, go for it.