As to your original question of payment offering, it sounds to me like you're perfectly on track. In my experience, someone who posts a friendly request and offers to pay a decent amount is fairly likely to get tons of free help.
What's annoying is when someone offers a really low amount (like 100k or something) and then gets really demanding about work getting done. It's like offering someone five dollars to clean your whole house, and then getting really nitpicky about how the work is done.
If one is being realistic, it's very unlikely that many people are ever going to be in the position to pay a perfectly "fair" wage for scripting. Any decently complicated script is going to take at least four hours of work including debugging and discussion of requirements, and $30/hr is really the lowest amount I can imagine anyone charging in an open market for programming services on a contract basis (and $80/hr is probably closer to the average), so we're talking about roughly 250 million meat being a "fair" price for a script. That never happens. So, while offering enough meat to get some interest (and show that the project is important to you) is necessary, it's remembering that the work done will still be roughly 90% on a "volunteer" basis that's really big. As long as you don't get the idea that by offering payment you now own the programmer's time completely*, you should be fine.
Just to be clear, I'm not suggesting you should offer more meat. I think your current offer is pretty much perfect. I'm just trying to say that, while it's a very decent amount of meat from the point of view of KoL, it isn't nearly on the level where you can think of the relationship with a programmer as a "strictly business" relationship. But as long as everyone remembers to have fun with things, and not get too serious, everything should be golden.
Sorry about the rambling! It's just that this comes up again and again, and your post was an open invitation to actually get some of these thoughts out. Too often, a person will offer a small amount of meat and then get very combative when anyone suggests doing anything different, or asks for more meat, etc. Thank you very much for being so considerate!
* This actually goes for "real world" contracting too. If you contract with someone, they get to choose when and how they do the work. You don't get to set their schedule, just their deadlines. If you don't like that, be prepared to hire them in, provide all of their equipment, electricity, the same level of benefits as your other employees, take care of all of the paperwork / tax issues for their wages, etc.
